proposition: Lemma coefC c i : c%:P`_i = if i == 0 then c else 0.
proof: Proof. by rewrite polyseqC; case: i => [|[]]; case: eqP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)