Erdős problem 23 · problems.science

The blow-up of $C_5$ shows that the bound $n^2$ in Erdős Problem 23 is tight: any bipartite subgraph must omit at least $n^2$ edges.

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6 retained statements2415f78e850a

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FormalConjectures/ErdosProblems/

23.lean

Retained formal statement6 of 6

There exists a triangle-free graph on $25$ vertices such that at least $25$ edges must be removed to make it bipartite. The balanced blow-up of $C_5$ with five parts of size $5$ witnesses this.

FormalConjectures/ErdosProblems/23.leanErdos23.erdos_23.variants.n5_tight1 lineExact file

1∃ G, G.CliqueFree 3 ∧ ∀ H ≤ G, H.IsBipartite → 25 ≤ (G.edgeFinset \ H.edgeFinset).card

SolvedStatement only, no proof

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