proposition: Lemma polyC_inj : injective polyC.
proof: Proof. by move=> c1 c2 eqc12; have:= coefC c2 0; rewrite -eqc12 coefC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)