proposition: Lemma polyCK : cancel polyC (coefp 0).
proof: Proof. by move=> c; rewrite [coefp 0 _]coefC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)