Sum of integers below 379

Proved

FiniteTriangular.sum_range_379

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

arithmeticfinite-sum

The sum of the nonnegative integers strictly less than $379$ equals $71631$ . Equivalently, $\\sum_{k=0}^{379-1} k = 379(379-1)/2$ .

Preamble

import Mathlib
open Finset

Formal statement

namespace FiniteTriangular

theorem sum_range_379 : ∑ k ∈ range 379, k = 71631 := 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.