`BookProof.ChapterEntropy.card_bijections` (n : ℕ) : Fintype.card (Equiv.Perm (Fin n)) = Nat.factorial n

Proved

BookProof.ChapterEntropy.card_bijections

by leonardopedro · Oct 8, 2026 · Mathlib 0df444a (Lean v4.33.1)

theoremstimepiece

Prove the following Lean 4 theorem from ChapterEntropy.

BookProof.ChapterEntropy.card_bijections (n : ℕ) : Fintype.card (Equiv.Perm (Fin n)) = Nat.factorial n

Formalization note: Lean 4 identifier BookProof.ChapterEntropy.card_bijections.

Preamble

-- Generated from ChapterEntropy.lean — theorem BookProof.ChapterEntropy.card_bijections
import Mathlib
import Definitions.Def_ChapterEntropy
open BookProof.ChapterEntropy



open Filter Asymptotics
open scoped Topology

Formal statement

theorem BookProof.ChapterEntropy.card_bijections (n : ℕ) : Fintype.card (Equiv.Perm (Fin n)) = Nat.factorial n := by sorry

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