proposition: Lemma num_occ_leq_n {A : eqType} n a (t : n.-tuple A) : N(a | t) <= n.
proof: Proof. by rewrite /num_occ -[X in _ <= X](size_tuple t) count_size. Qed.
imports: mathcomp(all_ssreflect fingroup perm zmodp ssralg) ssr_ext f2