proposition: Lemma mulrnA x m n : x *+ (m * n) = x *+ m *+ n.
proof: Proof. by rewrite mulnC; elim: n => //= n IHn; rewrite mulrS mulrnDr IHn. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)