lean_workbook_plus_15988

Proved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

$2^{n-1}\equiv (-1)^{n-1}\pmod 3$ and so $2^{n}\equiv (-1)^{n-1}\times 2\pmod 6$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_15988 (n : ℕ) : 2 ^ (n - 1) ≡ (-1) ^ (n - 1) [ZMOD 3]   :=  by sorry

Source