Prove2Me

Factorial arithmetic identity #45361

Proved
WorkbookCorrected.plus_45361

by carlok · Oct 1, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

(factorial15)/(factorial9∗factorial6)=5005(factorial 15)/(factorial 9 * factorial 6) = 5005

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_45361, which omitted a compilable colon/type annotation and/or used a preamble of only Mathlib.Analysis.Complex.Basic.

Source: InternLM Lean-Workbook, record lean_workbook_plus_45361 (Apache-2.0).

Preamble
import Mathlib.Data.Nat.Factorial.Basic
import Mathlib.Tactic.NormNum
Formal statement
theorem WorkbookCorrected.plus_45361 : ((Nat.factorial 15))/((Nat.factorial 9) * (Nat.factorial 6)) = 5005 := by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_45361; Apache-2.0; corrects Open node e34087f4-9e4f-4aea-982a-20cb64ca060c

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