proposition: Lemma size_polyXn n : size 'X^n = n.+1.
proof: Proof. by rewrite polyseqXn size_rcons size_nseq. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)