Sum of integers below 896

Proved

FiniteTriangular.sum_range_896

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

arithmeticfinite-sum

The sum of the nonnegative integers strictly less than $896$ equals $400960$ . Equivalently, $\\sum_{k=0}^{896-1} k = 896(896-1)/2$ .

Preamble

import Mathlib
open Finset

Formal statement

namespace FiniteTriangular

theorem sum_range_896 : ∑ k ∈ range 896, k = 400960 := 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.