proposition: Lemma tvec_sub n : (3 * (3 ^ n).-1.+1 = 3 ^ (n.+1) )%N.
proof: Proof. by rewrite -exp3n expnS. 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)