Prove2Me

Binomial coefficient identity #31830

Proved
WorkbookCorrected.plus_31830

by carlok · Sep 29, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

Nat.choose(6+4−1)4=126Nat.choose (6 + 4 - 1) 4 = 126

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_31830, 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_31830 (Apache-2.0).

Preamble
import Mathlib.Data.Nat.Choose.Basic
import Mathlib.Tactic.NormNum
Formal statement
theorem WorkbookCorrected.plus_31830 : (Nat.choose (6 + 4 - 1) 4) = 126 := by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_31830; Apache-2.0; corrects Open node e23cfee3-fbb1-49be-8753-1fe6901a11a1

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