proposition: Lemma polyseqXsubC a : 'X - a%:P = [:: - a; 1] :> seq R.
proof: Proof. by rewrite -['X]mul1r -polyCN -cons_poly_def polyseq_cons polyseq1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)