proposition: Lemma map_perm_mx (s : 'S_n) : (perm_mx s)^f = perm_mx s.
proof: Proof. by apply/matrixP=> i j; rewrite !mxE rmorph_nat. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)