Binomial coefficient identity #246

Proved

WorkbookCorrected.plus_246

by carlok · Sep 30, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

(Nat.choose (4+218-1) 218) = 1774630

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_246, 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_246 (Apache-2.0).

Preamble

import Mathlib.Data.Nat.Choose.Basic
import Mathlib.Tactic.NormNum

Formal statement

theorem WorkbookCorrected.plus_246 : (Nat.choose (4+218-1) 218) = 1774630 := by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_246; Apache-2.0; corrects Open node 0e92b179-2070-472c-a0e4-22030b4535eb

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