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Erdős problem 835

Does there exist a k>2k>2 such that the kk-sized subsets of {1,...,2k} can be coloured with k+1k+1 colours such that for every A{1,,2k}A\subset \{1,\ldots,2k\} with A=k+1\lvert A\rvert=k+1 all k+1k+1 colours appear among the kk-sized subsets of AA?

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13 retained statements2415f78e850a

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FormalConjectures/ErdosProblems/

835.lean

Retained formal statement1 of 13

It is known that for 3k83 \leq k \leq 8, the chromatic number of J(2k,k)J(2k, k) is greater than k+1k+1, see [Johnson graphs](https://aeb.win.tue.nl/graphs/Johnson.html).

FormalConjectures/ErdosProblems/835.leanErdos835.chromaticNumber_johnson_2k_k_lower_bound1 lineExact file
∀ {k : ℕ}, 3 ≤ kk ≤ 8 → ↑k + 1 < (SimpleGraph.johnson (2 * k) k).chromaticNumber
SolvedStatement only, no proof

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