Prove2Me

Factorial arithmetic identity #4730

Proved
WorkbookCorrected.plus_4730

by carlok · Sep 22, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

2005∗2004∗2003/3!=2∗5∗167∗401∗20032005 * 2004 * 2003 / 3! = 2 * 5 * 167 * 401 * 2003

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_4730, 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_4730 (Apache-2.0).

Preamble
import Mathlib.Data.Nat.Factorial.Basic
import Mathlib.Tactic.NormNum
Formal statement
theorem WorkbookCorrected.plus_4730 : 2005 * 2004 * 2003 / (Nat.factorial 3) = 2 * 5 * 167 * 401 * 2003 := by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_4730; Apache-2.0; corrects Open node e17106d9-2278-4962-83a7-5de217ae525c

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