proposition: Lemma order_eq1 x : (#[x] == 1%N) = (x == 1).
proof: Proof. by rewrite -trivg_card1 cycle_eq1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)