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Erdős problem 1023

Let F(n)F(n) be the maximal size of a family of subsets of {1,,n}\{1,\ldots,n\} such that no set in this family is the union of other members of the family. Is it true that there is a constant c>0c>0 such that F(n)c2nn1/2?F(n)\sim c \frac{2^n}{n^{1/2}}?

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FormalConjectures/ErdosProblems/

1023.lean

Retained formal statement1 of 3

Let F(n)F(n) be the maximal size of a family of subsets of {1,,n}\{1,\ldots,n\} such that no set in this family is the union of other members of the family. Is it true that there is a constant c>0c>0 such that F(n)c2nn1/2?F(n)\sim c \frac{2^n}{n^{1/2}}?

Hunter observes in the comments that this follows from the solution to [447], which implies F(n)(nn/2)F(n)\sim \binom{n}{n/2}.

FormalConjectures/ErdosProblems/1023.leanErdos1023.erdos_10231 lineExact file
True ↔ ∃ c, 0 < cAsymptotics.IsEquivalent Filter.atTop (fun n => ↑(Erdos1023.F n)) fun n => c * 2 ^ n / ↑n ^ (1 / 2)
SolvedProof has a holelean4external proof

The proof uses `sorry`: part of the argument is written but not proved. Lean accepts the file; it does not accept the theorem.

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