proposition: Lemma binn n : 'C(n, n) = 1.
proof: Proof. by elim: n => [|n IHn] //; rewrite binS bin_small. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div fintype tuple finfun bigop prime finset)