Prove2Me

Elementary arithmetic identity #65916

Proved
WorkbookCorrected.plus_65916

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

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

1+3+6+10+15+21+28+36+45+55+66+78+91+105+120+136+153+171=11401 + 3 + 6 + 10 + 15 + 21 + 28 + 36 + 45 + 55 + 66 + 78 + 91 + 105 + 120 + 136 + 153 + 171 = 1140

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_65916, 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_65916 (Apache-2.0).

Preamble
import Mathlib.Tactic.NormNum
Formal statement
theorem WorkbookCorrected.plus_65916 : 1 + 3 + 6 + 10 + 15 + 21 + 28 + 36 + 45 + 55 + 66 + 78 + 91 + 105 + 120 + 136 + 153 + 171 = 1140 := by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_65916; Apache-2.0; corrects Open node bb40de6e-2c7d-4a38-981b-fa7290c68998

View graph