proposition: Lemma center1 : 'Z(1) = 1 :> {set gT}.
proof: Proof. exact: gF1. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient action gproduct gfunctor) mathcomp(cyclic)