proposition: Lemma rpredMn n : {in S, forall u, u *+ n \in S}.
proof: Proof. by move=> u Su; rewrite -(card_ord n) -sumr_const rpred_sum. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)