English

Exact Values and Bounds for Ramsey Numbers of $C_4$ Versus a Star Graph

Combinatorics 2024-09-20 v1

Abstract

The 8 unknown values of the Ramsey numbers R(C4,K1,n)R(C_4,K_{1,n}) for n37n \leq 37 are determined, showing that R(C4,K1,27)=33R(C_4,K_{1,27}) = 33 and R(C4,K1,n)=n+7R(C_4,K_{1,n}) = n + 7 for 28n3328 \leq n \leq 33 or n=37n = 37. Additionally, the following results are proven: \bullet If nn is even and n\lceil\sqrt{n}\rceil is odd, then R(C4,K1,n)n+nn+2+1R(C_4,K_{1,n}) \leq n + \left\lceil\sqrt{n-\lceil\sqrt{n}\rceil+2}\right\rceil + 1. \bullet If m2(mod 6)m \equiv 2 \,(\text{mod } 6) with m8m \geq 8, then R(C4,K1,m2+3)m2+m+4R(C_4,K_{1,m^2+3}) \leq m^2 + m + 4. \bullet If R(C4,K1,n)>R(C4,K1,n1)R(C_4,K_{1,n}) > R(C_4,K_{1,n-1}), then R(C4,K1,2n+1R(C4,K1,n))nR(C_4,K_{1,2n+1-R(C_4,K_{1,n})}) \geq n.

Keywords

Cite

@article{arxiv.2409.12770,
  title  = {Exact Values and Bounds for Ramsey Numbers of $C_4$ Versus a Star Graph},
  author = {Luis Boza},
  journal= {arXiv preprint arXiv:2409.12770},
  year   = {2024}
}