proposition: Lemma coefXn n i : 'X^n`_i = (i == n)%:R.
proof: Proof. by elim: n i => [|n IHn] [|i]; rewrite ?coef1 // exprS coefXM ?IHn. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)