proposition: Lemma Tnk2_n0 n: Tnk2 n 0 = catalan n.
proof: Proof. by rewrite /Tnk2 subn0 muln1 addn0 addn1. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype) mathcomp(ssrnat seq path div) mathcomp(fintype tuple finfun bigop finset binomial)