Lean-Workbook Plus 52753: Penultimate binomial coefficient

Proved

WorkbookRestored.plus_52753

by wamlart · Sep 12, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

lean-workbookrestored-importssource-checked

For every positive integer $n$ , $\binom{n}{n-1}=n$ .

Source: Lean-Workbook row lean_workbook_plus_52753 (Apache-2.0). The unchanged proposition comes from the original record; its missing mathematical imports and namespaces are restored here.

Preamble

import Mathlib.Data.Nat.Choose.Basic
open Nat

Formal statement

theorem WorkbookRestored.plus_52753 (n : ℕ) (h : n ≠ 0) : choose n (n-1) = n   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_52753; immutable original Prove2Me node 88d77509-4952-46d0-80b3-2c841d15065e

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