lean_workbook_plus_29310

Proved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

Prove the combinatoric identity: $\binom{2n}{2} = 2.\binom{n}{2} + n^2$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_29310 (n : ℕ) : (2 * n).choose 2 = 2 * n.choose 2 + n ^ 2   :=  by sorry

Source