Sum of integers below 902

Proved

FiniteTriangular.sum_range_902

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

arithmeticfinite-sum

The sum of the nonnegative integers strictly less than $902$ equals $406351$ . Equivalently, $\\sum_{k=0}^{902-1} k = 902(902-1)/2$ .

Preamble

import Mathlib
open Finset

Formal statement

namespace FiniteTriangular

theorem sum_range_902 : ∑ k ∈ range 902, k = 406351 := 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.