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