proposition: Lemma length_maxperm : length (@maxperm n) = 'C(n, 2).
proof: Proof. by rewrite /length invset_maxperm card_Delta. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr