Sum of integers below 523

Proved

FiniteTriangular.sum_range_523

by carlok · Sep 25, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticfinite-sum

The sum of the nonnegative integers strictly less than $523$ equals $136503$ . Equivalently, $\\sum_{k=0}^{523-1} k = 523(523-1)/2$ .

Preamble

import Mathlib
open Finset

Formal statement

namespace FiniteTriangular

theorem sum_range_523 : ∑ k ∈ range 523, k = 136503 := by sorry

end FiniteTriangular

Source

Elementary arithmetic series: the sum of the first m positive integers is m(m+1)/2, rewritten on Finset.range.