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Keywords:
$(G,H)$-good coloring; Ramsey number; mixed anti-Ramsey number; Turán number
Summary:
Given two graphs $G$ and $H$, an edge-coloring of the complete graph $K_n$ is called a $(G,H)$-good coloring if it contains neither a monochromatic copy of $G$ nor a rainbow copy of $H$. Let $R(n;G,H)$ denote the set of integers $k$ for which a $(G,H)$-good $k$-coloring of $K_n$ exists. The numbers $\max R(n;G,H)$ and $\min R(n;G,H)$ are called the mixed anti-Ramsey numbers. We determine these numbers for $G = 2K_2$ and $H = K_s$ with $3\le s\le n$. We show that $\min R(n;2K_2,K_s)=n-2$ for all $s$. For $\max R(n;2K_2,K_s)$, we prove that if $s=2k+1$ then $\max R(n;2K_2,K_s) = t_n^k + n - k$, where $t_n^k$ is the Tuán number for $K_{k+1}$. If $s=2k+2$ and $s > \sqrt {2n-{7\over 4}}+ {1\over 2}$, then $\max R(n;2K_2,K_s) = t_{n-1}^k + 2n - k - 2$. The latter result reveals a connection between $\max R$ and the Turán number of $K_{\lfloor {s-1\over 2}\rfloor }$.
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