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Lean-Workbook Syntax 68270: The sum of the first four positive integers

Proved
WorkbookSyntax.plus_68270

by wamlart · Sep 12, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

lean-workbookrepaired-notationsource-checked

∑k=14k=10\sum_{k=1}^{4}k=10.

Source: Lean-Workbook row lean_workbook_plus_68270 (Apache-2.0), original record. This corrected declaration replaces the obsolete finite sum/product binder in with ∈ and restores required imports or namespaces. Ranges, casts, quantifiers, and mathematical expressions are preserved.

Preamble
import Mathlib.Algebra.BigOperators.Intervals
Formal statement
theorem WorkbookSyntax.plus_68270 : ∑ k ∈ Finset.Icc 1 4, k = 10   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_68270; immutable original Prove2Me node 43d407f2-22af-465d-87c0-dd4acf6274e8

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