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Erdős Problems


The Erdős problems are a large collection of questions posed or promoted by Paul Erdős and his collaborators (Bloom 2026). They range across number theory, combinatorics, graph theory, geometry, and related areas. Bloom's online Erdős Problems database listed 1221 numbered problems as of Oct. 26, 2026, together with their sources, status, references, and discussion. The numbers are database identifiers rather than established names for the individual questions.

The following table lists all 1221 problem numbers, using standard names where available and brief descriptions otherwise. Links identify existing coverage of the named problem or mathematical topic (Bloom 2026).

problemname or description
1Erdős distinct subset sums problem
2minimum modulus of a covering system
3Erdős-Turán conjecture
4large gaps between consecutive primes
5limit points of normalized prime gaps
6three successively increasing prime gaps
7distinct covering systems with odd moduli
8covering systems with monochromatic moduli
9odd integers not expressible as a prime and two powers of 2
10representations as a prime and boundedly many powers of 2
11odd integers as a squarefree number and a power of 2
12infinite sets avoiding divisors of sums of larger elements
13finite sets avoiding divisors of sums of larger elements
14integers with nonunique or missing two-term sum representations
15convergence of an alternating prime series
16odd integers outside prime-plus-power-of-2 representations
17even differences of primes below a prime bound
18number of divisors needed in practical-number representations
19Erdős-Faber-Lovász conjecture
20sunflower conjecture
21small intersecting families with large covering number
22Ramsey-Turán problem for 4-cliques
23making triangle-free graphs bipartite by edge deletion
24pentagon counts in triangle-free graphs
25logarithmic density outside truncated residue classes
26divisors drawn from a translate of an infinite set
27almost covering systems with comparable moduli
28Erdős-Turán additive basis conjecture
29explicit additive bases with few representations
30error term for the largest finite Sidon set
31additive complements of density zero
32sparse additive complements of the primes
33minimum growth of additive complements of the squares
34distinct consecutive sums in permutations
35Schnirelmann density growth under addition of a basis
36minimum overlap problem
37lacunary essential components for Schnirelmann density
38density-increasing shifts from a set that is not a basis
39dense infinite Sidon sets
40density thresholds for unbounded additive representation counts
41density of sets with distinct three-term sums
42Sidon sets with disjoint nonzero difference sets
43sizes of two Sidon sets with disjoint nonzero differences
44extending finite Sidon sets to large Sidon sets
45monochromatic Egyptian fractions using divisors of one integer
46monochromatic Egyptian fraction representations of 1
47Egyptian fractions in sets with large reciprocal sums
48common values of the totient and divisor-sum functions
49large sets on which the totient function increases
50derivatives of the totient-ratio distribution function
51large least preimages of totient values
52sum-product problem
53many subset sums or subset products
54growth of Ramsey 2-complete sets
55growth of Ramsey complete sets for more colors
56largest sets without many pairwise coprime elements
57reciprocal sums of odd cycle lengths in infinitely chromatic graphs
58chromatic bounds from the number of odd cycle lengths
59counting forbidden-subgraph graphs (four-cycle case: square-free graph)
604-cycle counts just above the extremal threshold
61Erdős-Hajnal conjecture
62common high-chromatic subgraphs of uncountably chromatic graphs
63power-of-2 cycle lengths in infinitely chromatic graphs
64Erdős-Gyárfás conjecture
65reciprocal sums of cycle lengths in dense graphs
66logarithmic asymptotics for additive representation counts
67Erdős discrepancy problem
68irrationality of the reciprocal factorial-minus-one series
69irrationality of the binary prime-factor-count series
70partition relations for triples at the continuum
71cycles with lengths in a prescribed arithmetic progression
72zero-density sets meeting cycle-length sets of dense graphs
73near-bipartiteness forced by large independent sets in subgraphs
74infinitely chromatic graphs with nearly bipartite finite subgraphs
75large independent sets in finite subgraphs of uncountably chromatic graphs
76edge-disjoint monochromatic triangles in two-colored complete graphs
77exponential growth rate of diagonal Ramsey numbers
78explicit exponential lower bounds for Ramsey numbers
79minimal obstructions to Ramsey size linearity
80large books in dense graphs whose edges lie in triangles
81clique partitions of chordal graphs
82large regular induced subgraphs
83bounds for doubly intersecting uniform set families
84number of possible sets of graph cycle lengths
85monotonicity of the minimum-degree threshold for 4-cycles
864-cycle-free subgraphs of hypercube graphs
87Ramsey lower bounds in terms of chromatic number
88induced subgraphs with prescribed edge counts in Ramsey graphs
89Erdős distinct distances problem
90Erdős unit distance problem
91nonuniqueness of point sets minimizing distinct distances
92many equal distances from every point
93distinct distances in convex polygons
94second moments of distance multiplicities in convex polygons
95second moments of planar distance multiplicities
96unit distances in convex polygons
97vertices with small distance multiplicities in convex polygons
98distinct distances without collinear triples or concyclic quadruples
99unit equilateral triangles in minimum-diameter point packings
100diameter bounds for point sets with separated distances
101four-point lines without five collinear points
102many rich lines forcing a richer line
103number of incongruent minimum-diameter point packings
104unit circles through at least three given points
105lines through one point set avoiding another
106sum of side lengths in square packings
107happy end problem
108high-girth subgraphs of high-chromatic graphs
109Erdős sumset conjecture
110small finite subgraphs of uncountably chromatic graphs
111edge deletions making finite subgraphs bipartite
112independent sets versus transitive subtournaments
113bipartite extremal numbers and 2-degeneracy
114Erdős-Herzog-Piranian conjecture (polynomial level curves)
115derivative bounds on connected polynomial lemniscates
116area enclosed by polynomial lemniscates
117covering groups by Abelian subgroups
118infinite partition relations for complete graphs
119growth of products with zeros on the unit circle
120Erdős similarity conjecture
121sets avoiding square products of odd lengths
122local concentration of shifted integers
123primitive representations using three coprime bases
124additive representations with restricted base expansions
125density of sums of restricted ternary and quaternary integers
126prime divisors of products of pairwise sums
127improvements to lower bounds for maximum cuts
128triangles forced by dense half-size subgraphs
129multicolor Ramsey bounds with one missing clique color
130coloring integer-distance graphs of planar point sets
131sets avoiding divisibility of sums of other elements
132distances with few representations in planar point sets
133maximum degree in triangle-free graphs of diameter 2
134completing triangle-free graphs to diameter 2
135distinct distances under four-point restrictions
136edge colorings with at least five colors on every four vertices
137powerful products of consecutive integers
138growth of two-color van der Waerden numbers
139Szemerédi's theorem
140bounds for three-term-progression-free sets
141consecutive primes in arithmetic progression
142asymptotics for progression-free subsets of intervals
143sparsity of separated real multiples
144integers with two divisors within a factor of 2
145moments of gaps between squarefree numbers
146Erdős degeneracy conjecture
147extremal lower bounds from bipartite minimum degree
148counting Egyptian fraction representations of 1
149Erdős-Nešetril conjecture (strong edge coloring)
150number of minimal vertex cuts
151clique transversals and triangle-free independence numbers
152isolated sums in Sidon sumsets
153mean square gaps in Sidon sumsets
154distribution of large Sidon sumsets modulo integers
155local growth of the largest Sidon set
156small maximal Sidon sets
157Sidon sets that are additive bases of order 3
158density of generalized Sidon sets
159Ramsey numbers for a 4-cycle versus a clique
160colorings with at least three colors in every four-term progression
161jumps in hypergraph coloring thresholds
162logarithmic thresholds for locally balanced edge colorings
163Burr-Erdős conjecture
164Erdős primitive set conjecture
165asymptotics for triangle-versus-clique Ramsey numbers
166lower bounds for 4-clique-versus-clique Ramsey numbers
167Tuza's conjecture
168largest sets avoiding a number with its double and triple
169reciprocal sums of progression-free sets
170sparse ruler problem
171density Hales-Jewett theorem
172Hindman's finite sums and products conjecture
173monochromatic triangles in two-colored planes
174characterization of Euclidean Ramsey sets
175Erdős squarefree conjecture
176discrepancy bounds for finite arithmetic progressions
177discrepancy controlled by the common difference
178simultaneous discrepancy bounds for countably many sequences
179many short progressions forcing a longer one
180Erdős-Simonovits compactness conjecture
181linear Ramsey bounds for hypercube graphs
182edge bounds forcing regular subgraphs
183growth of multicolor triangle Ramsey numbers
184Erdős-Gallai cycle decomposition conjecture
185Moser's cube problem (density-zero assertion)
186growth of nonaveraging sets
187long monochromatic progressions with prescribed differences
188red unit distances versus blue unit-step progressions
189monochromatic rectangles of every area
190monochromatic or rainbow arithmetic progressions
191monochromatic cliques with large logarithmic weights
192three-term progressions in positive lattice walks
193three collinear points in walks with finitely many steps
194monotone progressions in arbitrary orderings of the reals
195monotone progressions in permutations of the integers
196monotone four-term progressions in permutations of positive integers
197partitioning positive integers into progression-avoiding permutations
198infinite progressions in complements of Sidon sets
199infinite progressions outside three-term-progression-free real sets
200length of the longest arithmetic progression of primes
201large progression-free subsets of arbitrary integer sets
202number of disjoint residue classes with bounded moduli
203compositeness of all shifted multiples of powers of 2 and 3
204nearly disjoint covering systems using divisors of one integer
205sums of a power of 2 and an integer with few prime factors
206eventual greediness of best Egyptian fraction underapproximations
207Steiner triple systems of arbitrarily large girth
208gaps between squarefree numbers
209ordinary triangles in line arrangements
210number of ordinary lines through planar points
211lines determined by point sets with bounded collinearity
212Erdős-Ulam problem (dense rational distances)
213integral-distance point sets in general position
214unit squares outside unit-distance-free sets
215sets meeting the integer lattice once under every rigid motion
216empty convex polygons in planar point sets
217planar crescent configurations
218comparisons and equalities of consecutive prime gaps
219Green-Tao theorem
220second moments of gaps between reduced residues
221sparse additive complements of powers of 2
222gaps between sums of two squares
223number of diameter pairs in finite point sets
224obtuse angles in large point sets
225integral bounds for real-rooted trigonometric polynomials
226entire functions preserving rationality in both directions
227maximal terms versus maximum modulus of entire functions
228flat Littlewood polynomials on the unit circle
229entire functions with derivatives vanishing on prescribed discrete sets
230maximum-modulus lower bounds for unimodular polynomials
231Abelian squares in finite words
232maximum density of measurable unit-distance-free sets
233second moments of prime gaps
234limiting distribution of normalized prime gaps
235limiting distribution of gaps between reduced primorial residues
236number of prime-plus-power-of-2 representations
237unbounded representation counts using a prime and a set element
238long sequences of consecutive primes with separated gaps
239mean values of sign-valued multiplicative functions
240diverging gaps in integers supported on an infinite prime set
241largest sets with unique three-term sums
242Erdős-Straus conjecture
243rational reciprocal sums with near-quadratic denominator growth
244density of primes plus geometric-sequence terms
245sumset growth for zero-density sets
246complete sequences generated by two coprime bases
247transcendence of sparse binary expansions
248uniform bounds for prime-factor counts after an integer
249irrationality of the binary totient series
250irrationality of the binary divisor-sum series
251irrationality of the binary prime series
252irrationality of factorial series with divisor-power sums
253completeness from small successive ratios and progression intersections
254completeness criteria using growth and fractional parts
255unbounded discrepancy on a fixed interval
256maximum modulus of products of binomials
257irrationality of reciprocal Mersenne subseries
258irrationality of divisor-count Cantor series
259irrationality of a squarefree-weighted binary series
260irrationality of weighted sparse binary series
261multiple representations by weighted binary reciprocals
262growth of universally irrational reciprocal sequences
263irrationality under asymptotically equivalent denominator perturbations
264irrationality under bounded denominator perturbations
265growth of denominator sequences with two rational reciprocal sums
266irrationality of some shifted reciprocal sum
267irrationality of lacunary Fibonacci reciprocal sums
268interior of the set of three shifted reciprocal sums
269irrationality of reciprocal least-common-multiple series over smooth numbers
270irrationality of reciprocal rising-product series
271Stanley sequences with prescribed second term
272set families with arithmetic-progression intersections
273covering systems with prime-minus-one moduli
274Herzog-Schönheim conjecture
275covering all integers from a long covered interval
276composite Fibonacci-type sequences without a finite prime cover
277large divisor sums without divisor-modulus covering systems
278extremal densities of unions of prescribed residue classes
279covering integers by truncated prime residue classes
280integers missed by sparse sequences of residue classes
281uniform finite approximation to density-one residue coverings
282termination of the odd greedy Egyptian fraction algorithm
283prescribed polynomial sums of Egyptian fraction denominators
284largest possible minimum Egyptian fraction denominator
285smallest possible maximum Egyptian fraction denominator
286Egyptian fraction representations with denominators in short intervals
287gaps between Egyptian fraction denominators
288integer reciprocal sums over two intervals
289unit reciprocal sums over separated intervals
290decreasing denominators of consecutive harmonic subsums
291cancellation in harmonic numbers written over least common multiples
292possible largest denominators in Egyptian fractions for 1
293least omitted denominator in fixed-length Egyptian fractions
294possible smallest denominators in bounded Egyptian fractions
295number of Egyptian fraction terms with large denominators
296disjoint Egyptian fraction representations with bounded denominators
297counting Egyptian fraction representations with bounded denominators
298Egyptian fractions in sets of positive density
299bounded-gap denominator sets without a unit reciprocal subsum
300largest bounded sets without a unit reciprocal subsum
301sets without a reciprocal equal to a reciprocal subsum
302sets without a reciprocal equal to two other reciprocals
303monochromatic solutions of the three-reciprocal equation
304length of Egyptian fraction representations of rationals
305largest denominators needed in Egyptian fraction representations
306Egyptian fractions with squarefree semiprime denominators
307products of prime reciprocal sums equal to 1
308least integer missed by bounded-denominator reciprocal sums
309counting integer values of bounded-denominator reciprocal sums
310reciprocal subsums with small denominators in dense sets
311approximating 1 by bounded-denominator reciprocal sums
312reciprocal subsums close to 1 in multisets
313infinitude of primary pseudoperfect numbers
314overshoot of harmonic interval sums above 1
315extremal denominator growth in infinite Egyptian fractions
316partitioning a reciprocal sum below 2 into sums below 1
317small nonzero signed harmonic sums
318zero signed reciprocal subsums in progressions and dense sets
319large minimal zero signed reciprocal sums
320number of distinct reciprocal subset sums
321sets with distinct reciprocal subset sums
322number of representations by powers of matching degree
323density of sums of powers with few summands
324polynomial value sets with distinct pairwise sums
325number of integers representable as three equal-degree powers
326minimal additive bases with quadratic growth
327sets avoiding pairs whose sum divides their product
328partitioning sets to reduce additive representation bounds
329limsup growth of infinite Sidon sets
330positive-density minimal additive bases
331common nonzero differences of two dense square-root-growth sets
332bounded gaps among infinitely repeated differences
333sparse sumset covers of zero-density sets
334representing integers as sums of two smooth numbers
335pairs of sets with additive sumset density
336comparison of exact and unrestricted additive basis orders
337unbounded doubling ratios of sparse additive bases
338restricted orders of additive bases
339density of restricted sums from additive bases
340growth of the Mian-Chowla sequence
341eventual periodicity of greedy sum-free sequences
342Ulam sequence problems
343arithmetic progressions among subset sums of dense multisets
344arithmetic progressions among subset sums of square-root-growth sets
345completeness thresholds for sequences of powers
346growth ratios of minimally robust complete sequences
347robust density-one subset sums with doubling growth
348completeness under prescribed numbers of deletions
349completeness of rounded geometric sequences
350reciprocal sums of sets with distinct subset sums
351completeness of polynomial values perturbed by reciprocals
352unit-area triangles in large measurable planar sets
353unit-area configurations in infinite-measure planar sets
354two rounded geometric sequences as weakly complete sequences
355rational intervals among reciprocal subsums of lacunary sequences
356many distinct consecutive sums of bounded integers
357long sequences with all consecutive sums distinct
358unbounded counts of consecutive-sum representations
359greedy sequences avoiding earlier consecutive sums
360coloring to avoid a prescribed monochromatic subset sum
361largest sets avoiding a prescribed subset sum
362bounds for equal subset-sum multiplicities
363square products over disjoint intervals of length at least 4
364three consecutive powerful numbers
365consecutive powerful numbers and Pell equations
366a powerful number followed by a cube-full number
367products of powerful parts of consecutive integers
368largest prime factors of two consecutive integers
369long runs of smooth consecutive integers
370consecutive integers with small largest prime factors
371distribution of comparisons of consecutive largest prime factors
372three decreasing consecutive largest prime factors
373factorials that are products of smaller factorials
374counting factorial square products by minimum length
375Grimm's conjecture
376central binomial coefficients coprime to 105
377reciprocals of primes missing from central binomial coefficients
378squarefree binomial coefficients in a row
379large prime-power factors throughout binomial rows
380counting integers in intervals with repeated greatest prime factors
381growth of the count of highly composite numbers
382lengths of intervals with repeated greatest prime factors
383largest prime factors near prime squares
384small prime factors of interior binomial coefficients
385composites near an integer relative to their least prime factors
386binomial coefficients that are products of consecutive primes
387Erdős-Graham binomial divisor problem
388equal products of disjoint consecutive-integer blocks
389divisibility between adjacent equal-length integer products
390factorial factorizations into distinct factors exceeding the argument
391largest possible least factor in fixed-length factorial factorizations
392fewest bounded factors in a factorial factorization
393factorial factorizations into distinct factors in short intervals
394average least starts of consecutive products divisible by an integer
395reverse Littlewood-Offord problem
396central binomial coefficients divisible by long terminal products
397equalities between products of distinct central binomial coefficients
398Brocard's problem
399factorials as sums or differences of two higher powers
400factorial divisibility and sums of factorial arguments
401large factorial arguments dividing a prime-weighted factorial
402Graham's GCD problem
403powers of 2 as sums of distinct factorials
404prime-power divisibility of sums of factorials
405prime powers as a factorial plus a power
406powers of 2 with only ternary digits 0 and 1
407bounded representation counts using powers of 2 and 3
408distribution of iterated totient stopping times
409primes reached by iterating the totient function plus 1
410growth of iterated divisor sums
411eventual doubling in iterated integer-plus-totient sequences
412intersections of iterated divisor-sum orbits
413barriers for an integer plus its distinct-prime-factor count
414intersections of integer-plus-divisor-count orbits
415ordering patterns of consecutive totient values
416asymptotic count of totient values
417comparison of two counting functions for totient values
418infinitely many noncototients
419limit points of consecutive factorial divisor-count ratios
420divisor-count ratios of nearby factorials
421density-one sequences with distinct consecutive products
422Hofstadter's Q-sequence
423growth of a greedy consecutive-sum sequence
424density of the closure under pairwise products minus 1
425multiplicative Sidon sets and distinct higher products
426graphs with many uniquely occurring subgraphs
427divisible sums of consecutive primes
428large sets of shifts simultaneously producing primes
429infinite admissible sets of prime-producing shifts
430composites in a greedy large-prime-factor sequence
431additive decomposition of the primes into two infinite sets
432density of sumsets with pairwise coprime elements
433largest Frobenius numbers with bounded generators
434generator sets maximizing the number of unrepresentable integers
435Frobenius numbers of binomial-coefficient generators
436least runs of consecutive higher-power residues
437many square partial products of increasing integers
438large sets whose sumset contains no square
439monochromatic pairs summing to a square or higher power
440growth of consecutive least common multiples
441largest sets with bounded pairwise least common multiples
442reciprocal least-common-multiple sums in sets with large reciprocal sums
443common products of two integers with prescribed sums
444large restricted divisor counts relative to reciprocal sums
445multiplicative inverses in short intervals modulo primes
446density of integers with divisors in a doubling interval
447largest union-free set families
448number of dyadic intervals occupied by divisors
449nearby divisor pairs relative to divisor counts
450local density of integers with divisors in a doubling interval
451prime factors of short products of consecutive integers
452long intervals of integers with many distinct prime factors
453prime squares versus symmetric prime products
454symmetric prime sums exceeding twice the central prime
455growth of convex sequences of primes
456least totient multiples versus least primes in progressions
457short consecutive products divisible by all small primes
458least-common-multiple growth between consecutive primes
459gaps between integers supported on primes dividing the endpoints
460reciprocal sums in a greedy pairwise-coprime construction
461distinct smooth parts in short intervals
462weighted sums of least prime factors in short intervals
463composites close to an integer relative to their least prime factors
464nondense irrational multiples of lacunary sequences
465upper bounds for planar sets avoiding near-integer distances
466large planar sets with all distances separated from integers
467two prime-residue coverings of a short interval
468new partial divisor sums and least representing integers
469reciprocal sums of primitive pseudoperfect numbers
470odd and primitive weird numbers
471unbounded prime sets closed under three-prime sums
472infinite greedy prime sequences formed from shifted sums
473permutations with consecutive terms summing to primes
474three-color partition relations for uncountable sets of reals
475ordering finite-field subsets with distinct partial sums
476Erdős-Heilbronn conjecture
477unique additive complements of polynomial value sets
478number of distinct factorial residues modulo a prime
479prescribed residues of powers of 2 modulo their exponents
480close pairs at fixed index gaps in bounded real sequences
481repetitions in recursively generated affine sequences
482Graham-Pollak sequences and binary digits
483growth of Schur numbers
484many monochromatic sums in finite colorings
485number of nonzero terms in polynomial squares
486logarithmic density outside truncated modular exclusions
487least-common-multiple triples in positive-density sets
488density ratios for sets of multiples
489second moments of gaps between integers avoiding sparse divisors
490product bounds for sets with distinct cross-products
491additive functions with bounded consecutive differences
492equidistribution within gaps of ratio-one sequences
493representing integers as a product minus a sum
494reconstructing finite complex sets from fixed-size subset sums
495Littlewood conjecture
496Diophantine approximation by an irrational quadratic form
497Dedekind numbers (Dedekind's problem)
498concentration of signed sums of complex numbers
499large diagonal products in doubly stochastic matrices
500Turán's tetrahedron problem
501independent sets for bounded small-measure set mappings
502maximum size of two-distance sets
503maximum size of sets with every triangle isosceles
504large angles forced by finite planar point sets
505Borsuk's conjecture
506minimum number of determined circles
507Heilbronn triangle problem
508Hadwiger-Nelson problem
509covering polynomial lemniscates by circles with small total radius
510negative values of cosine sums with distinct integer frequencies
511large connected components of polynomial lemniscates
512Littlewood's exponential sum problem
513maximal-term ratios for transcendental entire functions
514paths of rapid growth for transcendental entire functions
515integrable reciprocal powers along paths to infinity
516minimum and maximum modulus of lacunary entire functions
517value distribution of lacunary entire functions
518covering two-colored complete graphs by same-color paths
519lower bounds for complex power sums
520iterated-logarithm law for random multiplicative functions
521almost-sure real-root counts for random Littlewood polynomials
522zeros of random Littlewood polynomials in the unit disk
523maximum modulus of random Littlewood polynomials
524maximum on the real unit interval of random sign polynomials
525minimum modulus of typical Littlewood polynomials
526almost-sure coverage of the circle by random arcs
527boundary convergence of random power series
528connective constants for self-avoiding walks
529displacement of random self-avoiding walks
530large Sidon subsets of arbitrary finite real sets
531finite bounds for monochromatic subset sums
532Hindman's theorem
533large triangle-free subsets of dense graphs without 5-cliques
534largest pairwise noncoprime sets containing the upper endpoint
535sets avoiding equal pairwise greatest common divisors
536sets without triples having equal pairwise least common multiples
537prime-multiple coincidences in dense sets
538reciprocal sums under bounded prime-multiple representation counts
539number of distinct quotients by pairwise greatest common divisors
540Olson constant
541residue sequences with zero sums of only one length
542reciprocal sums of sets with large pairwise least common multiples
543random subset sums covering finite Abelian groups
544differences of consecutive triangle-versus-clique Ramsey numbers
545graphs maximizing Ramsey numbers for a fixed edge count
546Ramsey bounds in terms of edge count
547tree Ramsey numbers bounded by twice the vertex count minus 2
548Erdős-Sós theorem (former tree conjecture)
549Ramsey numbers of trees with unequal bipartition classes
550tree-versus-multipartite-graph Ramsey bounds
551cycle-versus-clique Ramsey numbers
5524-cycle-versus-star Ramsey numbers
553comparison of two- and three-color triangle Ramsey numbers
554multicolor odd-cycle versus triangle Ramsey growth
555multicolor even-cycle Ramsey numbers
556three-color cycle Ramsey bounds
557multicolor tree Ramsey bounds
558multicolor complete-bipartite Ramsey numbers
559size Ramsey numbers of bounded-degree graphs
560size Ramsey numbers of balanced complete bipartite graphs
561size Ramsey numbers of star forests
562tower growth of uniform hypergraph Ramsey numbers
563thresholds for locally balanced edge colorings
564double-exponential lower bounds for 3-uniform Ramsey numbers
565exponential upper bounds for induced Ramsey numbers
566Ramsey size linearity for locally sparse graphs
567Ramsey size linearity for three specified graphs
568criteria for Ramsey size linearity from trees and cliques
569odd-cycle Ramsey bounds in terms of opposing edge count
570sharp cycle Ramsey bounds in terms of opposing edge count
571rational exponents conjecture
572extremal lower bounds for even cycles
573extremal graphs without triangles or 4-cycles
574extremal graphs without two consecutive odd-even cycle lengths
575extremal numbers for forbidden families containing a bipartite graph
576extremal numbers for hypercube graphs
577vertex-disjoint 4-cycle factors from a minimum-degree bound
578spanning hypercubes in random graphs
579large independent sets in dense graphs without K_(2,2,2)
580Loebl's conjecture
581largest bipartite subgraphs of triangle-free graphs
5824-clique-free graphs forcing monochromatic triangles
583Gallai's path decomposition conjecture
584dense subgraphs with pairs of edges on short common cycles
585edge bounds forcing two cycles on the same vertices
586covering systems with pairwise nondividing moduli
587large sets without square subset sums
588number of rich lines under bounded collinearity
589large subsets without collinear triples
590triangle partition relation at omega^omega
591triangle partition relation at omega^(omega^2)
592triangle partition relations for countable power-of-omega ordinals
593finite subhypergraphs forced by uncountable chromatic number
594large odd cycles in uncountably chromatic graphs
595countable triangle-free decompositions of 4-clique-free graphs
596finite-versus-countable edge-color Ramsey properties
597ordinal partition relations with forbidden subgraphs
598colorings of countable subsets realizing all colors on large sets
599Erdős-Menger theorem (former conjecture)
600edge thresholds forcing large books
601infinite paths or independent sets of prescribed ordinal type
602two-coloring almost disjoint countable families without singleton intersections
603chromatic bounds for countable sets without two-point intersections
604many distinct distances from one planar point
605superlinear repeated-distance counts on the sphere
606possible numbers of lines determined by planar points
607possible sets of line multiplicities in planar configurations
608edges lying in pentagons above the triangle threshold
609short monochromatic odd cycles in multicolor complete graphs
610upper bounds for clique transversal numbers
611clique transversals when all maximal cliques are large
612diameter bounds from minimum degree and forbidden cliques
613decomposition into a bipartite graph and a bounded-degree graph
614minimum edges forcing high degree in every small induced subgraph
615large independent sets near the 4-clique Ramsey-Turán threshold
616global transversals from local intersecting hypergraph conditions
617Erdős-Gyárfás balanced coloring conjecture
618completing low-degree triangle-free graphs to diameter 2
619completing connected triangle-free graphs to diameter 4
620large triangle-free induced subgraphs of 4-clique-free graphs
621Erdős-Gallai-Tuza conjecture
622many cycle-spanned subsets in dense regular graphs
623infinite free sets for finite-subset mappings
624thresholds for subset mappings realizing every value
625chromatic versus cochromatic numbers of random graphs
626asymptotic tradeoffs between graph girth and chromatic number
627maximum chromatic-to-clique-number ratio
628Erdős-Lovász Tihany conjecture
629small bipartite graphs with large list chromatic number
6303-choosability of planar bipartite graphs
6315-choosability of planar graphs
632multiples of graph list multicolorings
633triangles allowing only square numbers of congruent pieces
634possible numbers of congruent pieces in triangle dissections
635large sets avoiding divisibility by long differences
636many vertex-count and edge-count pairs in Ramsey graphs
637induced subgraphs with many distinct degrees in Ramsey graphs
638infinite-cardinal extensions of finite triangle-Ramsey families
639edges outside monochromatic triangles in two-colored complete graphs
640high-chromatic induced vertex sets of odd cycles
641many edge-disjoint cycles on the same vertices
642edge bounds when cycles have fewer chords than vertices
643equal unions of disjoint pairs of uniform hyperedges
644transversal bounds from locally two-pierceable set families
645monochromatic three-term progressions with large common difference
646factorials with even valuations at prescribed primes
647barriers for an integer plus its divisor count
648long decreasing subsequences of greatest prime factors
649prescribed greatest prime factors of consecutive integers
650many distinct multiples of distinct set elements in intervals
651higher-dimensional happy end problem bounds
652several points with few distinct distances
653many different pinned distance counts in one point set
654pinned Erdős distinct distances problem, no four concyclic points
655distinct distances under centered-circle restrictions
656shifted infinite restricted sumsets inside positive-density sets
657distinct distances in sets without isosceles triangles
658squares in dense subsets of the integer grid
659few global distances under four-point local restrictions
660distinct distances among convex polyhedron vertices
661few cross-distances between two large planar point sets
662triangular-lattice distance comparison (formulation unclear)
663least prime missing from a short consecutive product
664bounded-multiplicity transversals for nearly disjoint large sets
665pairwise balanced designs with large blocks
6666-cycle-free subgraphs of hypercubes
667clique-size exponents under local edge-density constraints
668nonuniqueness of point sets maximizing unit distances
669extremal numbers of lines through given numbers of points
670diameter of point sets with all distances mutually separated
671pointwise convergence and unbounded Lebesgue functions in interpolation
672perfect powers among products of arithmetic progressions
673sums of ratios of consecutive divisors
674products of self-powers equal to a self-power
675translation recurrence in arithmetic sets
676approximating integers by multiples of prime squares
677distinct least common multiples of equal-length disjoint intervals
678comparison of least common multiples of disjoint unequal intervals
679uniform prime-factor-count bounds before an integer
680nearby integers with large least prime factors
681nearby composites with large least prime factors
682rough composites inside prime gaps
683large prime factors of binomial coefficients
684growth of small-prime parts of binomial coefficients
685distinct prime-factor counts of binomial coefficients
686integers as ratios of equal-length consecutive products
687Jacobsthal function and prime-residue interval coverings
688covering intervals using only large prime moduli
689double coverings of intervals by prime residue classes
690unimodality of the distribution of the kth smallest prime factor
691criteria for sets of multiples to have density 1
692unimodality of the density of exactly one interval divisor
693gaps between integers with a divisor in a doubling interval
694ratios of greatest to least totient preimages
695growth of prime chains with successive divisibility
696lengths of divisor chains with successive congruences
697density thresholds for divisors in a prescribed residue class
698growing common divisors of pairs of binomial coefficients
699large common prime divisors of pairs of binomial coefficients
700common divisors of an integer and its binomial coefficients
701Chvátal's intersecting-family conjecture
702singleton intersections in large uniform set families
703set families avoiding a prescribed intersection size
704growth of higher-dimensional unit-distance chromatic numbers
7053-colorability of high-girth unit-distance graphs in the plane
706chromatic bounds for graphs defined by finitely many distances
707extending Sidon sets to perfect difference sets
708covering prescribed products by products from intervals
709distinct representatives divisible by prescribed integers
710short intervals containing distinct multiples of every small integer
711uniform interval bounds for distinct divisible representatives
712Turán densities of complete uniform hypergraphs
713power-law asymptotics and rational exponents for bipartite extremal numbers
714extremal lower bounds for balanced complete bipartite graphs
715cubic subgraphs of regular graphs
716Ruzsa-Szemerédi theorem ((6,3)-theorem)
717chromatic number versus largest topological clique
718quadratic degree bounds forcing complete graph subdivisions
719decomposing uniform hypergraphs into edges and small cliques
720size Ramsey numbers of paths and cycles
721off-diagonal van der Waerden numbers
722existence of Steiner systems under divisibility conditions
723prime power conjecture for finite projective planes
724many mutually orthogonal Latin squares
725asymptotic enumeration of Latin rectangles
726reciprocal sums of primes with residues in an upper half-interval
727factorial-square divisibility with shifted arguments
728factorial divisibility with sums of arguments exceeding the total
729factorial ratios with denominators supported on bounded primes
730central binomial coefficients with identical prime supports
731least nondivisor of a central binomial coefficient
732possible block-size sequences of pairwise balanced designs
733possible line-multiplicity sequences of planar point sets
734pairwise balanced designs with bounded block-size multiplicities
735magic configurations with positive point weights and equal line sums
736arbitrarily high chromatic graphs with prescribed finite subgraphs
737a fixed edge on all sufficiently long cycles
738induced trees in infinitely chromatic triangle-free graphs
739subgraphs with prescribed smaller infinite chromatic numbers
740preserving infinite chromatic number while eliminating short odd cycles
741partitioning sets while preserving positive sumset density
742Murty-Simon conjecture
743tree packing conjecture (Gyárfás-Lehel)
744edge deletions making chromatic-critical graphs bipartite
745second-largest components in critical random graphs
746Hamiltonian cycles in random graphs above the connectivity threshold
747perfect matching thresholds in random 3-uniform hypergraphs
748Cameron-Erdős conjecture
749almost-complete sumsets with bounded representation counts
750infinitely chromatic graphs with nearly half-sized independent sets
751widely separated cycle lengths in 4-chromatic graphs
752many cycle lengths from minimum degree and girth
753list chromatic numbers of a graph and its complement
754many equal distances from each point in four dimensions
755unit equilateral triangle counts in six dimensions
756many distances each occurring more often than the number of points
757large Sidon subsets under local difference-set constraints
758maximum cochromatic numbers of small graphs
759cochromatic numbers on surfaces of prescribed genus
760large cochromatic subgraphs of high-chromatic graphs
761dichromatic numbers versus chromatic and cochromatic numbers
762chromatic versus cochromatic numbers of 5-clique-free graphs
763Erdős-Fuchs theorem (bounded-error case)
764bounded-error linear growth of cumulative triple-sum counts
765asymptotic extremal number of the 4-cycle
766minimum extremal numbers for fixed vertex and edge counts
767edge bounds forcing cycles with many chords at one vertex
768density of integers with divisors congruent to 1 modulo their prime factors
769tiling cubes by prescribed numbers of smaller cubes
770common divisors of initial power-minus-one values
771large subsets avoiding any one prescribed sum
772large Sidon subsets of bounded-representation sets
773largest Sidon subsets of the squares
774partitioning proportionately dissociated sets into dissociated sets
775many maximal clique sizes in 3-uniform hypergraphs
776antichains with many sizes and prescribed size multiplicities
777edge counts of comparability graphs of set families
778clique-size and degree games on complete graph edges
779prime sums involving a primorial
780multicolor Ramsey numbers for uniform hypergraph matchings
781monochromatic descending waves
782quasi-progressions and additive cubes among squares
783minimizing uncovered integers for pairwise coprime divisor sets
784integers avoiding divisor sets with bounded reciprocal sums
785error terms for exact additive complements
786dense sets with uniquely determined product lengths
787large subsets with pairwise sums outside the original set
788subsets whose pairwise sums avoid a prescribed higher interval set
789maximum size of an admissible set
790large subsets avoiding equations between an element and distinct-element sums
791minimum size of additive two-bases for finite intervals
792large sum-free subsets of arbitrary integer sets
793sets avoiding divisibility by products of other elements
794small dense subhypergraphs above a tripartite edge threshold
795largest sets with distinct subset products
796large sets with bounded multiplicative representation counts
797acyclic chromatic number in terms of maximum degree
798covering integer grids by lines through selected grid points
799list chromatic number of typical graphs
800linear Ramsey bounds when high-degree vertices are nonadjacent
801small dense vertex sets forced by small independence number
802independent sets in clique-free graphs of prescribed average degree
803dense almost-regular subgraphs of prescribed size
804global independence bounds from local independent sets
805graphs with cliques and independent sets in every small vertex set
806small sumset covers of square-root-sized sets
807biclique partition number of random graphs
808sum-product bounds restricted to graph edges
809Burr-Erdős-Graham-Sós conjecture
810dense edge-colored graphs with every 4-cycle rainbow
811rainbow subgraphs in balanced complete graph colorings
812ratio and difference growth of consecutive diagonal Ramsey numbers
813large cliques when every seven vertices contain a triangle
814small high-minimum-degree induced subgraphs above degeneracy thresholds
815prescribed cycles in minimally non-2-degenerate graphs
816equal-degree endpoints of three-edge paths in dense graphs
817sets whose subset sums avoid arithmetic progressions
818large product sets from small sumsets
819largest truncated sumsets of square-root-sized sets
820coprime pairs of power-minus-one values
821large multiplicities of totient values
822density of the integer-plus-totient image
823ratios of integers with equal divisor sums
824counting coprime pairs with equal divisor sums
825sufficient abundance for pseudoperfectness
826uniform divisor-count bounds after an integer
827large subsets with all circumradii distinct
828totient divisibility of shifted arguments
829bounds for the number of two-cube representations
830infinitely many amicable pairs
831distinct circumradii determined by planar point triples
832minimum edge count for uniform hypergraphs of given chromatic number
833high-degree vertices in non-2-colorable uniform hypergraphs
8343-critical triple systems with large minimum degree
835subset colorings with every local palette complete in Johnson graphs
836intersecting non-2-colorable hypergraphs with large edge intersections
837jumping densities of 3-uniform hypergraphs
838number of convex subsets of planar point sets
839sparsity of sequences avoiding earlier consecutive sums
840largest quasi-Sidon subsets of intervals
841completing integers to squares using products of nearby integers
8423-coloring a Hamiltonian cycle with disjoint triangles
843Ramsey 2-completeness of the squares
844largest sets with no squarefree pairwise products
845density of sums of comparable integers supported on 2 and 3
846finite partitions into sets without collinear triples
847finite partitions into three-term-progression-free sets
848largest sets whose pairwise products plus 1 are not squarefree
849prescribed multiplicities among binomial coefficients
850Erdős-Woods conjecture (three-term version)
851almost-all representations by a power of 2 and an almost prime
852long runs of distinct prime gaps
853least missing even prime gap
854missing and distinct gaps between reduced primorial residues
855second Hardy-Littlewood conjecture
856reciprocal sums without equal pairwise least common multiples
857Erdős-Szemerédi sunflower conjecture
858reciprocal sums of sets avoiding rough integer ratios
859density of integers representing a target by distinct divisors
860short intervals with distinct representatives divisible by small primes
861enumeration of Sidon sets relative to their maximum size
862enumeration of maximal Sidon sets
863comparison of bounded sum-representation and difference-representation sets
864large sets with only one repeated pair sum
865three elements and all their pair sums inside a dense set
866pair-sum cliques inside dense integer sets
867large sets avoiding membership of consecutive sums
868minimal additive subbases from diverging representation counts
869minimal subbases in unions of disjoint additive bases
870minimal higher-order subbases under logarithmic representation bounds
871partitioning rich additive bases into two bases
872length of the primitive-set selection game
873counts of bounded least common multiples of consecutive set elements
874largest sets with disjoint subset-sum lengths
875growth and gaps of infinite sets with disjoint subset-sum lengths
876gaps in infinite sets avoiding distinct-element sum equations
877enumeration of maximal sum-free sets
878extremal sums of coprime integers with prescribed prime support
879maximum sums of pairwise coprime bounded integers
880bounded gaps among restricted sums from additive bases
881deleting infinite sets from minimal higher-order bases
882sets whose nonempty subset sums form a primitive set
883odd cycles and tripartite subgraphs in coprimality graphs
884reciprocal divisor differences versus consecutive divisor differences
885common differences between factor pairs of distinct integers
886few divisors just above the square root
887uniform divisor bounds in short intervals above the square root
888sets where square quadruple products force equal cross-products
889unbounded new prime factors along consecutive integers
890prime-factor counts in blocks of consecutive integers
891integers with many prime factors in primorial-length intervals
892growth and density criteria for primitive sequences
893growth of cumulative Mersenne divisor counts
894colorings avoiding lacunary differences
895independent Schur triples in triangle-free graphs
896products with unique cross-factor representations
897large consecutive jumps of additive functions
898Erdős-Mordell theorem
899difference-set growth of zero-density sets
900long paths in supercritical random graphs
901minimum edges in non-2-colorable uniform hypergraphs
902minimum tournament size with all small sets externally dominated
903gaps in block counts above projective plane designs
904large degree sums on cliques at the Turán threshold
905large books above the triangle extremal threshold
906dense zero sets along every infinite subsequence of derivatives
907decomposing functions with continuous differences
908decomposing functions with measurable differences
909spaces whose squares have the same positive finite dimension
910proper nonhomeomorphic connected subsets of Euclidean connected sets
911superlinear size Ramsey bounds from high average degree
912distinct exponents in prime factorizations of factorials
913consecutive-integer products with distinct prime exponents
914Hajnal-Szemerédi theorem
915many disjoint paths between two vertices above an edge threshold
916cycles with an external vertex adjacent to three cycle vertices
917maximum edge counts in chromatic-critical graphs
918infinite chromatic number with smaller subgraphs countably colorable
919chromatic number versus ordinal type in infinite graphs
920high-chromatic graphs avoiding a fixed clique
921largest odd girth for fixed chromatic number
922chromatic bounds from nearly half-sized independent sets in subgraphs
923high-chromatic triangle-free subgraphs
924clique-free graphs forcing monochromatic cliques
925large independent sets in graphs not Ramsey for triangles
926extremal numbers for augmented subdivided cliques
927number of distinct maximal clique sizes
928joint distribution of consecutive greatest prime factors
929small primes covering blocks of consecutive integers
930perfect powers among products over disjoint long intervals
931disjoint consecutive products with the same prime factors
932multiple smooth integers inside prime gaps
933large 2-and-3-smooth parts of consecutive-integer products
934distant edges forced by edge count and maximum degree
935powerful parts of products of consecutive integers
936powerful neighbors of powers of 2 and factorials
937four-term progressions of coprime powerful numbers
938three-term progressions of consecutive powerful numbers
939additive relations between coprime higher-powerful numbers
940sums of higher-powerful numbers, including cube-full numbers
941representing large integers as three powerful numbers
942powerful numbers between consecutive squares
943number of representations as two powerful numbers
944vertex-critical graphs with no small critical edge sets
945long runs of distinct divisor counts
946Erdős-Mirsky conjecture
947Mirsky-Newman theorem
948growth bounds for subset sums missing a color
949large pair-sum sets outside real sum-free sets
950reciprocal distances to preceding primes
951counting multiplicatively independent generators of separated products
952Gaussian moat problem
953measure of planar sets without integer distances
954error bounds for a greedy cumulative pair-sum construction
955Erdős-Granville-Pomerance-Spiro conjecture
956unit separations between disjoint translates of a convex set
957product of shortest- and longest-distance multiplicities
958characterizing point sets with consecutive distance multiplicities
959gap between the two largest distance multiplicities
960cliques of ordinary lines under bounded collinearity
961maximum runs of smooth consecutive integers beyond the smoothness bound
962long consecutive blocks each with a prime factor exceeding the length
963large subsets with distinct subset sums in arbitrary real sets
964density of ratios of consecutive divisor counts
965uncountable sets with monochromatic restricted pair sums
966Ramsey progression-free sets forcing shorter monochromatic progressions
967zero-free Dirichlet series with positive reciprocal coefficients
968density of increases in the nth prime divided by its index
969error term in counting squarefree integers
970growth of the Jacobsthal function by number of prime factors
971large least primes in many residue classes
972prime values of irrational multiples of primes rounded down
973exponentially small consecutive complex power sums
974repeated zero blocks in power sums forcing roots of unity
975average divisor counts of irreducible polynomial values
976greatest prime factors of products of polynomial values
977growth of greatest prime factors of Mersenne numbers
978power-free values of irreducible polynomials
979unbounded representation counts by matching-degree prime powers
980average least higher-power nonresidues over primes
981average thresholds for cancellation in quadratic character sums
982many distinct distances from a convex polygon vertex
983small prime supports containing many set elements
984colorings with short monochromatic progressions relative to their starts
985prime primitive roots below every prime modulus
986lower bounds for off-diagonal clique Ramsey numbers
987large Fourier sums at some integer frequency
988unbounded spherical cap discrepancy
989disk-counting discrepancy of infinite planar sequences
990angular distribution of polynomial roots in terms of sparsity
991equidistribution of sphere points maximizing products of distances
992metric discrepancy bounds for integer sequences
993unimodality of independent-set sequences of forests
994metric equidistribution in measurable sets for irrational rotations
995metric sums of square-integrable functions along lacunary sequences
996Fourier approximation criteria for lacunary equidistribution
997failure of well-distribution for prime multiples
998bounded remainder intervals for irrational rotations
999Duffin-Schaeffer conjecture
1000vanishing average proportions of new reduced denominators
1001limiting measures of rational approximation over denominator intervals
1002limiting distribution of logarithmically normalized fractional-part sums
1003equal totients of consecutive integers
1004long runs of distinct totient values
1005local ordering of Farey numerators and denominators
1006acyclic orientations remaining acyclic after any single reversal
1007fewest edges in a graph of Euclidean dimension 4
1008large 4-cycle-free subgraphs of arbitrary graphs
1009packing edge-disjoint triangles above the extremal threshold
1010triangle counts just above the extremal threshold
1011edge thresholds forcing triangles at prescribed chromatic number
1012long cycles forced by edge counts
1013minimum order of triangle-free graphs with prescribed chromatic number
1014ratios of consecutive off-diagonal Ramsey numbers
1015covering vertices by disjoint monochromatic cliques
1016minimum edge counts of pancyclic graphs
1017clique partition numbers of dense graphs
1018bounded-size nonplanar subgraphs of dense graphs
1019large maximal planar subgraphs above an edge threshold
1020Erdős matching conjecture
1021extremal numbers for subdivided complete graphs
1022property B from local sparsity of large set families
1023families with no member a union of other members
1024independent sets in linear triple systems
1025large free sets for pair-to-element mappings
1026large sums on monotone subsequences
1027many two-colorings avoiding monochromatic edges in uniform hypergraphs
1028discrepancy of signed pairs on induced vertex sets
1029improving the probabilistic lower bound for diagonal Ramsey numbers
1030ratios of nearly diagonal Ramsey numbers
1031nontrivial regular induced subgraphs of Ramsey graphs
1032large minimum degree in edge-critical 4-chromatic graphs
1033large triangle degree sums above the extremal threshold
1034triangles with many vertices adjacent to two of their vertices
1035spanning hypercubes from large minimum degree
1036exponentially many nonisomorphic induced subgraphs of Ramsey graphs
1037large homogeneous sets from nearly distinct vertex degrees
1038length of real polynomial sublevel sets with bounded real roots
1039large disks inside polynomial lemniscates
1040area of polynomial lemniscates versus transfinite diameter
1041short root-connecting paths inside polynomial lemniscates
1042components of polynomial lemniscates versus transfinite diameter
1043short projections of polynomial lemniscates
1044longest component boundaries of polynomial lemniscates
1045maximum product of distances under a diameter bound
1046enclosing disks for connected polynomial lemniscates
1047convexity of small polynomial sublevel components
1048large lemniscate components from bounded roots
1049irrationality of rational-parameter Lambert series
1050irrationality of the reciprocal power-of-2-minus-3 series
1051irrationality of reciprocal products with doubly exponential growth
1052finiteness of unitary perfect numbers
1053abundancy ratios of multiply perfect numbers
1054least integers with prescribed sums of their smallest divisors
1055recursive classes defined by prime factors of a prime plus 1
1056consecutive interval products congruent to 1 modulo a prime
1057growth of the count of Carmichael numbers
1058factorials plus 1 supported on two nearby primes
1059primes remaining composite after subtracting any smaller factorial
1060multiplicities of the integer-times-divisor-sum map
1061additive coincidences of the divisor function
1062largest sets without an element dividing two others
1063binomial coefficients divisible by almost all numerator-block terms
1064totient comparisons after subtracting the totient
1065primes with prime odd parts after subtracting 1
1066large independent sets in planar contact graphs
1067infinitely connected uncountably chromatic subgraphs
1068countable infinitely connected subgraphs of uncountably chromatic graphs
1069Szemerédi-Trotter theorem
1070large unit-distance-free subsets of arbitrary planar point sets
1071maximal disjoint families of unit segments
1072least factorials congruent to minus 1 modulo primes
1073composite divisors of factorials plus 1
1074residue restrictions on prime divisors of factorials plus 1
1075jumping hypergraph densities above the multipartite threshold
1076extremal triple systems avoiding k vertices with k-2 edges
1077large dense almost-regular subgraphs
1078cliques forced by high multipartite minimum degree
1079dense neighborhoods in graphs at clique extremal thresholds
10806-cycles in unbalanced bipartite graphs
1081density of sums of two powerful numbers
1082distinct and pinned distances without collinear triples
1083minimum distinct distances in higher dimensions
1084contact number problem
1085unit-distance counts in higher dimensions
1086maximum number of equal-area triangles
1087quadruples containing repeated distances
1088large subsets with all pairwise distances distinct
1089point-set sizes forcing prescribed numbers of distances
1090finite point sets forcing rich monochromatic lines
1091chords in odd cycles of 4-chromatic graphs
1092global chromatic bounds from nearly colorable finite subgraphs
1093deficiency of binomial coefficients without small prime factors
1094least prime factors of binomial coefficients
1095least binomial coefficients with no small prime factors
1096gaps between sums of powers of a real base near 1
1097distinct common differences of three-term progressions
1098clique bounds for noncommuting graphs of groups
1099sums of powers of relative gaps between consecutive divisors
1100coprime consecutive divisor pairs
1101gaps in integers avoiding sparse pairwise coprime divisors
1102growth of shift sets with squarefree exclusion or recurrence
1103growth of infinite sets with squarefree sumsets
1104maximum chromatic number of triangle-free graphs
1105anti-Ramsey numbers of paths and cycles
1106distinct prime factors of partition-function values
1107representing integers by boundedly many higher-powerful numbers
1108perfect powers and powerful numbers among distinct factorial sums
1109largest finite sets with squarefree sumsets
1110primitive additive representations using two coprime bases
1111anticomplete high-chromatic sets in graphs of bounded clique number
1112bounded-gap sequences whose iterated sumsets avoid lacunary sets
1113Sierpiński numbers without finite prime covering sets
1114spacing of critical points for equally spaced real roots
1115short paths of growth to infinity for entire functions
1116incomparable counting functions for distinct meromorphic values
1117number of maximum-modulus points on circles
1118growth of entire functions with finite-area superlevel sets
1119cardinality of families of entire functions with few pointwise values
1120short paths from the origin to the unit circle in polynomial lemniscates
1121enclosing circles for nonseparable circle families
1122additive functions decreasing on a zero-density set
1123nonisomorphism of Boolean algebras modulo density ideals
1124Tarski's circle-squaring problem
1125monotonicity from a three-point functional inequality
1126almost-everywhere solutions of Cauchy's functional equation
1127countable partitions of Euclidean space into distinct-distance sets
1128countably infinite monochromatic boxes in uncountable products
1129interpolation nodes minimizing the Lebesgue constant
1130local maxima of interpolation Lebesgue functions
1131minimum integrated squares of Lagrange basis polynomials
1132pointwise logarithmic growth of interpolation Lebesgue functions
1133large norms forced by nearly full interpolation
1134density of the closure under three affine maps
1135Collatz conjecture
1136dense sets with no pair summing to a power of 2
1137adjacent prime-gap products versus maximum prime gaps
1138prime counts on the scale of maximum prime gaps
1139large gaps between integers with at most two prime factors
1140integers remaining prime after subtracting twice any smaller square
1141integers remaining prime after coprime square subtractions
1142integers remaining prime after every smaller power-of-2 subtraction
1143minimum prime-multiple counts in short intervals
1144large positive fluctuations of random completely multiplicative sums
1145representation counts for asymptotically equal additive complements
1146essential-component property of integers supported on 2 and 3
1147additive bases defined by quadratic Diophantine approximation
1148bounded representations as two squares minus a square
1149coprimality of integers with their rounded noninteger powers
1150uniform maximum-modulus lower bounds for Littlewood polynomials
1151prescribed limit sets for interpolation at Chebyshev nodes
1152almost-everywhere divergence of near-degree interpolation
1153local lower bounds for interpolation Lebesgue functions
1154Hausdorff dimensions of subrings and subfields of the reals
1155random triangle removal process
1156concentration of chromatic numbers of random graphs
1157extremal hypergraphs avoiding prescribed vertex and edge counts
1158extremal lower bounds for complete multipartite uniform hypergraphs
1159bounded-intersection blocking sets in projective planes
1160maximal counts of groups of bounded order
1161most frequent element orders in symmetric groups
1162enumeration and order distribution of symmetric-group subgroups
1163arithmetic structure of symmetric-group subgroup orders
1164fully covered disks of 2-dimensional random walks
1165number of favorite sites of 2-dimensional random walks
1166number of sites ever favorite in 2-dimensional random walks
1167negative stepping-up problem
1168negative countable-color partition relations without continuum assumptions
1169triangle partition relations for the square of the first uncountable ordinal
1170consistency of strong partition relations below the second uncountable ordinal
1171finite-color partition relations at the square of the first uncountable ordinal
1172ordinal partition relations under the generalized continuum hypothesis
1173large free sets for almost disjoint set mappings
1174clique-free graphs forcing countably colored monochromatic cliques
1175uncountably chromatic triangle-free subgraphs
1176edge colorings realizing every edge color within some vertex color
1177forbidden finite subhypergraphs at uncountable chromatic numbers
1178Brown-Erdős-Sós conjecture for uniform hypergraphs
1179uniform representation counts for random subset sums in finite groups
1180bounded sums of inverses of small residues modulo primes
1181least primes missing from logarithmic-length consecutive products
1182triangle-good connected graphs and their edge counts
1183large monochromatic families with union and intersection closure
1184large-prime-factor counts in polynomial-scale intervals
1185long progressions with common differences from a prescribed difference set
1186density of monochromatic arithmetic progressions
1187monochromatic prime progressions and prime common differences
1188enumeration of minimal distinct covering systems
1189irreducible covering modulus sets
1190reciprocal sums of large disjoint congruence moduli
1191logarithmic improvements in infinite Sidon set density
1192additive bases with small mean-square representation counts
1193density of equality to a monotone representation-count function
1194growth in perfect difference bases
1195measure growth of real sets avoiding integer ratios
1196weighted reciprocal sums of primitive sets with large minimum element
1197integer dilates of positive-measure sets meeting scaled integers
1198monochromatic sums of disjoint products from an infinite set
1199infinite sets with monochromatic sumsets
1200prime-residue interval coverings with bounded reciprocal modulus sum
1201large prime factors in almost all long consecutive products
1202integers avoiding half the residues for each prescribed prime
1203large normalized prime-factor counts after an integer
1204minimum diameter and mean of admissible prime-tuples
1205maximal uniform multiplicity of residue coverings
1206large Sidon subsets of the cubes
1207large subsets without isosceles triangles
1208large subsets with all distances distinct
1209prime or squarefree translates of fast-growing sequences
1210reciprocal distances from an endpoint to pairwise coprime integers
1211logarithmic density of monochromatic subset sums
1212infinite paths through visible lattice points avoiding prime pairs
1213repeated consecutive sums in long bounded-gap sequences
1214identical prime supports of all power-minus-one sequences
1215short paths in sublevel sets for polynomials with roots on the unit circle
1216large transitive subtournaments
1217long divisibility chains in sets of positive logarithmic density
1218negative triple partition relations under the generalized continuum hypothesis
1219partition relations for sums of increasing cardinal exponentials
1220partition relations at aleph_0-inaccessible singular cardinals
1221extremal spacing ratios of circular sequences

Recent results on individual problems include the following.

For problem 30, Carter et al. (2026) improved the error-term coefficient in the upper bound for the maximum size of a Sidon set in {1,...,N}. This does not settle whether every positive power N^epsilon is an admissible error bound.

Problem 59 concerns enumeration of graphs with a forbidden subgraph. Yang (2026) established the case of labeled square-free graphs. This does not resolve the general formulation.

Problem 138 concerns the growth of two-color van der Waerden numbers. The three-color numerical improvements of Kim (2026) concern a different parameter choice and do not settle that problem.

Problem 302 asks how large a subset A subset= {1,...,n} can be if no distinct a,b,c in A satisfy 1/a=1/b+1/c. Writing f(n) for the maximum cardinality, the problem asks in particular whether f(n)=(1/2+o(1))n, with o(1) as in little-O notation (Erdős and Graham 1980, Bloom 2026). A Lean development directed by Sodelin (2026), with the argument, code, and formalization produced by ChatGPT/Codex, reported f(732)=f(731), f(733)=f(732)+1, and f(734)=f(732)+2. The first relation follows from an isolated component in the hypergraph of forbidden triples containing the five vertices 122, 183, 244, 366, and 732. Every admissible selection from this component contains at most three of them and can be replaced by 122, 183, and 244. Exact certificates show that neither 733 nor 734 belongs to a forbidden triple on {1,...,734}. The values of f(n) for n=1, 2, ... begin 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 10, 10, 11, ... (OEIS A390395). This tabulation reaches f(731)=606, so the relations above give f(732)=606, f(733)=607, and f(734)=608. The development proves the three relations but not the external value f(731)=606. As of Sep. 25, 2026, independent human review had not established either that the formal statement matches the classical problem or that the finite result is new. The asymptotic Problem 302 remained open (VibeMathed 2026c).

Problem 433 concerns the largest Frobenius number for a fixed number of generators bounded by a parameter N. Its asymptotic value was proved by Dixmier (1990). Chen et al. (2026) obtained a sharp finite upper bound for individual generating sets.

Problem 793 asks for the maximum cardinality F(n) of a subset A of {1,...,n} such that abc whenever a, b, and c are distinct members of A. The recorded question is whether F(n)=pi(n)+(C+o(1))n^(2/3)(lnn)^(-2) for some constant C. Bloom (2026) reports that GPT-5.6 Sol, prompted by Przemek Chojecki, gave a Lean-verified argument with

 F(n)=pi(n)+((27)/2+o(1))(n^(2/3))/((lnn)^2).

Here pi(n) is the prime counting function, and o(1) denotes a quantity tending to 0 as n->infty in little-O notation. This determines the proposed constant as C=27/2 (Bloom 2026, VibeMathed 2026b). No independent specialist review had been reported as of Sep. 9, 2026.

Problem 940 asks, for every integer r>=3, whether infinitely many positive integers are not sums of at most r r-full, or r-powerful, numbers, meaning numbers m such that p|m implies p^r|m for every prime number p. It also asks whether the integers representable by at most r such summands have natural density zero (Bloom 2026). For r=3, the summands are cube-full numbers. Beyer de Ryke (2026) proved the stronger conclusion that the positive integers not representable by at most three cube-full numbers have positive lower natural density. This resolves the first question for r=3, while the density-zero question for r=3 remains open.

Problem 1154 concerns the possible Hausdorff dimensions of subfields of R. Assuming the axiom of constructibility V=L for the constructible universe, Wang (2026) constructed proper subfields of R that are coanalytic sets with every Hausdorff dimension in [0,1]. The unrestricted existence question in ZFC remains open.

For an integer k>=1, let n_k be the least integer n>2k such that the product (n-k)(n-k+1)...(n-1) has no prime factor in the interval (k,2k). Erdős (1979) conjectured that n_k grows faster than every fixed power of k. Van Doorn and Tang (2026) reported the stronger bound

 n_k>exp((ln^2k)/(20lnlnk))

for all sufficiently large k. The paper credits ChatGPT 5.5 Pro with the core idea of adapting Konyagin's argument and supplies supporting Lean formalizations produced by Aristotle. Independent specialist review and an external audit of the formalization had not been reported as of Sep. 21, 2026 (VibeMathed 2026a).

Problem 682 concerns gaps between consecutive primes in which every intervening integer has a least prime factor smaller than the gap. Mossinghoff and Trudgian (2026) obtained a conditional counting asymptotic for these gaps, assuming the Dickson-Hardy-Littlewood prime-tuples conjecture.

Problem 789 asks for large admissible sets, whose subset sums determine the number of summands. The Erdős-Nicolas-Sárközy conjecture instead counts all such subsets of {1,...,N}.


See also

Burr-Erdős-Graham-Sós Conjecture, Cube-Full Number, Erdős Distinct Subset Sums Problem, Erdős-Gallai Cycle Decomposition Conjecture, Erdős-Graham Binomial Divisor Problem, Erdős-Gyárfás Balanced Coloring Conjecture, Erdős-Hajnal Conjecture, Erdős-Mahler Conjecture, Erdős-Moser Equation, Erdős Similarity Conjecture, Erdős-Straus Conjecture, Erdős Unit Distance Problem, Factorial Square Product, Frobenius Number, Littlewood Polynomial, Minimum Overlap Problem, Rational Exponents Conjecture, Sunflower Conjecture, Tuza's Conjecture, Unsolved Problems, van der Waerden Number

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References

Beyer de Ryke, B. "A Density Deficit for Sums of Three Cube-Full Numbers." 26 Jul 2026. https://arxiv.org/abs/2609.35772.Bloom, T. F. "Erdős Problems." Accessed Oct. 26, 2026. https://www.erdosproblems.com/.Carter, D.; O'Bryant, K.; and Tao, T. "On the Diameter and Distribution of Sidon Sets." 26 Oct 2026. https://arxiv.org/abs/2610.36207.Chen, L.; Hu, T.; Mao, Y.; and Zhang, G. "A Sharp Upper Bound for the Frobenius Number." 23 Oct 2026. https://arxiv.org/abs/2610.32219.Dixmier, J. "Proof of a Conjecture by Erdős and Graham Concerning the Problem of Frobenius." J. Number Th. 34, 198-209, 1990. https://doi.org/10.1016/0022-314X(90)90150-P.Erdős, P. "Some Unconventional Problems in Number Theory." Acta Math. Acad. Sci. Hungar. 33, 71-80, 1979.Erdős, P. and Graham, R. L. Old and New Problems and Results in Combinatorial Number Theory. Geneva, Switzerland: L'Enseignement Mathématique Université de Genève, Vol. 28, 1980.Kim, S. "Polychromatic Blocks and Explicit Lower Bounds for Multicolour van der Waerden Numbers." 22 Oct 2026. https://arxiv.org/abs/2610.32000.Mossinghoff, M. J. and Trudgian, T. S. "Frangible Prime Gaps." 25 Oct 2026. https://arxiv.org/abs/2610.34525.Sodelin. "Old Conjecture Probes: Finite Results for Erdős Problem 302." 2026. https://github.com/Sodelin/oldest-conjecture-/tree/ced445d951ea043fda41b03044192838a838b0f3.van Doorn, W. and Tang, Q. "Consecutive Integers Free of Certain Prime Factors." 18 Jun 2026. https://arxiv.org/abs/2606.19863.VibeMathed. "Erdős's Conjecture on Consecutive Integers Free of Certain Prime Factors." 18 Jun 2026a. https://vibemathed.com/problem/erdos-consecutive-integers-prime-factors.VibeMathed. "Erdős Problem 793." Sep. 9, 2026b. https://vibemathed.com/problem/erdos-793.VibeMathed. "Reciprocal-Triple-Free Sets: Finite Maxima through 734." Sep. 7, 2026c. https://vibemathed.com/problem/reciprocal-triple-free-sets-the-finite-plateau-at-732.Wang, Y. "Coanalytic Subfields of the Reals of Every Hausdorff Dimension." 7 Oct 2026. https://arxiv.org/abs/2610.09707.Yang, T. "The Number of C_4-Free Graphs." 29 Oct 2026. https://arxiv.org/abs/2610.39595.Sloane, N. J. A. Sequence A390395 in "The On-Line Encyclopedia of Integer Sequences."

Cite this as:

Weisstein, Eric W. "Erdős Problems." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ErdosProblems.html

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