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Goldbach Partition


A Goldbach partition of an even number 2n is an unordered pair of primes (p,q) such that 2n=p+q (Oliveira e Silva). Letting r(2n) denote the number of Goldbach partitions of 2n without regard to order, the number of ways of writing 2n as a sum of two prime numbers taking the order of the two primes into account, for n>=2, is

 R(2n)={2r(2n)-1   for n prime; 2r(2n)   for n composite.
(1)

The Goldbach conjecture is then equivalent to the statement that r(n)>0 or, equivalently, that R(n)>0, for every even integer n>2.

The r(n) and R(n) convention above is used by Oliveira e Silva. The NIST Digital Library of Mathematical Functions instead denotes by S(n) the number of unordered partitions into odd primes for even integers n>4. In analytic number theory, Bhowmik and Halupczok (2020) use g(n)=sum_(p_1+p_2=n)1, where the sum is over primes, for the ordered unweighted count. They use G(n)=sum_(a+b=n)Lambda(a)Lambda(b) for the weighted count, where Lambda(n) is the Mangoldt function, while Brüdern et al. (2019) denote this weighted function by R(n). Veritasium (2025) uses h(N) for the unordered partition count. This h is a local notation for Goldbach partitions and is unrelated to the standard functions omega(n) and Omega(n) that count prime factors.

For an even integer N>=4, each Goldbach partition determines a unique larger prime number p in the interval [N/2,N-2]. Consequently,

 r(N)<=pi(N-2)-pi((N-1)/2),
(2)

where pi(x) is the prime counting function. Equality holds iff N-p is a prime number for every prime number p in that interval. Deshouillers et al. (1993, p. 210) proved that 210 is the largest value of N attaining this upper bound. Here r(210)=19. Numberphile (2017) illustrates the equality case.

GoldbachPartition

A plot of r(2n), sometimes known as Goldbach's comet, for n up to 2000 is illustrated above.

For an integer n>=2, the cumulative number of Goldbach partitions is

 sum_(i=1)^nr(2i)=1+sum_(k=2)^(pi(n))[pi(2n-p_k)-(k-1)],
(3)

where p_k is the kth prime number (J. F. Martin, pers. comm., Dec. 4, 2010). The initial 1 counts 4=2+2. For each smaller odd prime p_k<=n, the summand counts the possible primes q with p_k<=q<=2n-p_k, so every remaining partition is counted exactly once.

The following table summarizes the values of several variants of r(n) for n=2, 4, ....

partition typeOEISvalues
p,q 1 or primeA0010311, 2, 2, 2, 2, 2, 3, 2, 3, 3, 3, 4, 3, ...
p,q primeA0459170, 1, 1, 1, 2, 1, 2, 2, 2, 2, 3, 3, 3, ...
p,q odd primeA0023750, 0, 1, 1, 2, 1, 2, 2, 2, 2, 3, 3, 3, ...

Various fractal properties have been observed in Goldbach's partition (Liang et al. 2006).


See also

Goldbach Conjecture, Goldbach Number, Prime Partition, Weak Goldbach Conjecture

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References

Bhowmik, G. and Halupczok, K. "Asymptotics of Goldbach Representations." In Various Aspects of Multiple Zeta Functions. Adv. Stud. Pure Math. 84. Tokyo, Japan: Mathematical Society of Japan, pp. 1-21, 2020. https://doi.org/10.2969/aspm/08410001.Brüdern, J.; Kaczorowski, J.; and Perelli, A. "Explicit Formulae for Averages of Goldbach Representations." Trans. Amer. Math. Soc. 372, 6981-6999, 2019. https://doi.org/10.1090/tran/7799.Clawson, C. Mathematical Mysteries: The Beauty and Magic of Numbers. New York: Plenum Press, p. 241, 1996.Deshouillers, J.-M.; Granville, A.; Narkiewicz, W.; and Pomerance, C. "An Upper Bound in Goldbach's Problem." Math. Comput. 61, 209-213, 1993. https://doi.org/10.1090/S0025-5718-1993-1202609-9.Doxiadis, A. Uncle Petros and Goldbach's Conjecture. Faber & Faber, 2001.Grave, D. A. Traktat z Algebrichnogo Analizu, Vol. 2. Kiev, Ukraine: Vidavnitstvo Akademiia Nauk, p. 19, 1938.Halberstam, H. and Richert, H.-E. Sieve Methods. New York: Academic Press, 1974.Lehmer, D. H. Guide to Tables in the Theory of Numbers. Bulletin No. 105. Washington, DC: National Research Council, p. 80, 1941.Liang, W.; Yan, H.; and Zhi-cheng, D. "Fractal in the Statistics of Goldbach Partition." 12 Jan 2006. https://arxiv.org/abs/nlin/0601024.National Institute of Standards and Technology. "Goldbach Conjecture." §27.13(ii) in Digital Library of Mathematical Functions. https://dlmf.nist.gov/27.13#ii.Numberphile. "210 Is Very Goldbachy." Featuring C. Pomerance. May 28, 2017. https://www.youtube.com/watch?v=PEMIxDjSRTQ.Oliveira e Silva, T. "Goldbach Conjecture Verification." https://sweet.ua.pt/tos/goldbach.html.Sinisalo, M. K. "Checking the Goldbach Conjecture up to 4·10^(11)." Math. Comput. 61, 931-934, 1993.Veritasium. "The Obviously True Theorem No One Can Prove." Jun. 20, 2025. https://www.youtube.com/watch?v=x32Zq-XvID4.Sloane, N. J. A. Sequences A001031/M0213, A002375/M0104, and A045917 in "The On-Line Encyclopedia of Integer Sequences."

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Goldbach Partition

Cite this as:

Weisstein, Eric W. "Goldbach Partition." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/GoldbachPartition.html

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