proposition: Lemma binS n m : 'C(n.+1, m.+1) = 'C(n, m.+1) + 'C(n, m).
proof: Proof. by []. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div fintype tuple finfun bigop prime finset)