Elementary arithmetic identity #9626

Proved

WorkbookCorrected.plus_9626

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

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

9 + 36 + 84 + 126 + 126 + 84 + 36 + 9 + 1 = 511

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_9626, 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_9626 (Apache-2.0).

Preamble

import Mathlib.Tactic.NormNum

Formal statement

theorem WorkbookCorrected.plus_9626 : 9 + 36 + 84 + 126 + 126 + 84 + 36 + 9 + 1 = 511 := by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_9626; Apache-2.0; corrects Open node 2d04e382-6afb-48b5-8910-6b95c0b77da1

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