Open Research Index

All-ones polynomials over GF(2) under the substitution X ↦ X² + X + 1 (OEIS A071642, TheoremDB P12771)

Brandon Yates

Palomar Registrypalomar/PALOMAR-2026-09-11-000004Sep 11, 2026math.NTscore 0

Formalizes in Lean 4 the resolution of a 2019 OEIS conjecture of L. H. Gallardo (comment on A071642; TheoremDB P12771): for every n ≥ 2 the all-ones polynomial 1 + X + ⋯ + Xⁿ is irreducible over GF(2) if and only if 1 + P + ⋯ + Pⁿ is irreducible over GF(2), where P = X² + X + 1. The compared statements are the per-n equivalence, the literal set-level form of the OEIS comment (the terms ≥ 2 coincide), and the failure of the excluded case n = 1. The proof is elementary: a factorization of the all-ones polynomial composes to one of the substituted polynomial; conversely irreducibility forces n…

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