A sum of residues of powers of two

Proved

WorkbookSyntax.plus_42290

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

lean-workbookrepaired-notationsource-checked

$\sum_{k=0}^{19}(2^k\bmod25)=250$ .

Notation repair: Replaced the obsolete finite-sum binder “in” with the current “∈” notation. The ranges, summands, hypotheses and conclusion are unchanged.

Source: Lean-Workbook record lean_workbook_plus_42290 (Apache-2.0). Original declaration.

Preamble

import Mathlib
open Nat

Formal statement

theorem WorkbookSyntax.plus_42290 :
  ∑ k ∈ (Finset.range 20), (2^k) % 25 = 250   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, record lean_workbook_plus_42290; finite-sum notation repair; Apache-2.0

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