A five-term arithmetic sum

Proved

WorkbookSource.problem_7918

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

We get a sum: $1 + 56 + 111 + 166 + 221 = 555$

Source: InternLM Lean-Workbook, record lean_workbook_7918 (Apache-2.0). The complete source proposition and explicit variable declarations are preserved.

Preamble

import Mathlib
open Real Nat

Formal statement

theorem WorkbookSource.problem_7918 :
  1 + 56 + 111 + 166 + 221 = 555  :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, record lean_workbook_7918; Apache-2.0

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