proposition: Lemma ffact_small n m : n < m -> n ^_ m = 0.
proof: Proof. by rewrite ltnNge -ffact_gt0; case: posnP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div fintype tuple finfun bigop prime finset)