proposition: Lemma monic_Xn_sub_1 n : n > 0 -> 'X^n - 1 \is monic.
proof: Proof. move=> n_gt0; rewrite monicE lead_coefE size_Xn_sub_1 // coefB. by rewrite coefXn coef1 eqxx eqn0Ngt n_gt0 subr0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)