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Casey Tompkins, On graphs without cycles of length 0 modulo 4
Casey Tompkins, On graphs without cycles of length 0 modulo 4
Bollobás proved that for every $k$ and $\ell$ such that $k\mathbb{Z}+\ell$ contains an even number, an $n$-vertex graph containing no cycle of length $\ell \bmod k$ can contain at most a linear number of edges. The precise (or asymptotic) value of the maximum number of edges in such a graph is known for very few …