proposition: Lemma prodrXl n I r (P : pred I) (F : I -> R) : \prod_(i <- r | P i) F i ^+ n = (\prod_(i <- r | P i) F i) ^+ n.
proof: Proof. by rewrite (big_morph _ (exprMn n) (expr1n _ n)). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)