proposition: Lemma fromNat_mulBn n m1 m2 : #m1 *# m2 = fromNat (n:=n) (m1 * m2).
proof: Proof. apply toNat_inj. rewrite toNat_mulB !toNat_fromNat. by rewrite modnMm. Qed.
imports: HB(structures) mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq fintype tuple zmodp div) ssrextra.tuple ssrextra.nat spec spec.properties operations mathcomp(ssralg)