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Theorems · Theorem · combinatorics

IsAntichain.sperner

∀ {α : Type u_2} [inst : Fintype α] {𝒜 : Finset (Finset α)},
  IsAntichain (fun x1 x2 => x1 ⊆ x2) ↑𝒜 → 𝒜.card ≤ (Fintype.card α).choose (Fintype.card α / 2)

Sperner's theorem. The size of an antichain in Finset α is bounded by the size of the maximal layer in Finset α. This precisely means that Finset α is a Sperner order.

Defined in
Mathlib.Combinatorics.SetFamily.LYM
Cited by
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Foundations
Depth 90 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
Fintype

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