TOPICS
Search

Generalized Schur Number


The generalized Schur number s_a(r) associated with the linear equation

 x+ay=z

is the least positive integer N such that every assignment of r colors to the integers 1, ..., N contains a solution with x, y, and z of the same color (Khamseh 2020). The parameters a and r are positive integers, and the variables in a solution need not be distinct.

For a=1, this least-endpoint convention gives s_1(r)=S(r)+1, where S(r) is the Schur number defined as the largest interval admitting a coloring without a monochromatic solution.

Khamseh and Safareh (2026) proved

 s_a(3)=a^3+5a^2+7a+1

for every integer a>=2. Equivalently, for k>=3, the least endpoint for the equation x+(k-1)y=z is T_k(3)=k^3+2k^2-2. The values for k=3, 4, ... are 43, 94, 173, 286, 439, ... (OEIS A083074). If u(n)=n^3-n^2-n-1 denotes the OEIS indexing starting at n=0, then T_k(3)=u(k+1). The proof combines an explicit coloring for the lower bound with a finite symbolic case analysis for the upper bound. The accompanying checking program has not been independently replayed here.


See also

Linear Equation, Schur Number, Schur's Problem

Explore with Wolfram|Alpha

References

Khamseh, A. "On Generalized Schur Numbers of the Equation x+ay=z." J. Math. 2020, 7069730, 2020. https://doi.org/10.1155/2020/7069730.Khamseh, A. and Safareh, M. H. "The Three-Color Generalized Schur Number of x+(k-1)y=z: A Proof for All k from a Critical Set of 33 Polynomials." 1 Nov 2026. https://arxiv.org/abs/2611.01714v1.Sloane, N. J. A. Sequence A083074 in "The On-Line Encyclopedia of Integer Sequences."

Cite this as:

Weisstein, Eric W. "Generalized Schur Number." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/GeneralizedSchurNumber.html

Subject classifications