proposition: Lemma mul3n n : (3 * n = n + (n + n))%N.
proof: Proof. by rewrite !mulSn addn0. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice path fintype) mathcomp(div bigop order ssralg poly polydiv ssrnum perm zmodp ssrint) mathcomp(polyorder polyrcf interval matrix mxtens)