Erdős Problem #809

declared status 'open'. Formalized: no. Let $k\geq 3$ and define $F_k(n)$ to be the minimal $r$ such that there is a graph $G$ on $n$ vertices with $\lfloor n^2/4\rfloor+1$ many edges such that the edges can be $r$-coloured so that every subgraph isomorphic to $C_{2k+1}$ has no colour repeating on the edges. Is it true that$$F_k(n)\sim n^2/8?$$ Prize: no. Tags: graph theory, ramsey theory.

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