Sum of integers below 169

Proved

FiniteTriangular.sum_range_169

by carlok · Sep 24, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticfinite-sum

The sum of the nonnegative integers strictly less than $169$ equals $14196$ . Equivalently, $\sum_{k=0}^{169-1} k = 169(169-1)/2$ .

Preamble

import Mathlib
open Finset

Formal statement

namespace FiniteTriangular

theorem sum_range_169 : ∑ k ∈ range 169, k = 14196 := 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.