proposition: Lemma ucn_id n G : 'Z_n('Z_n(G)) = 'Z_n(G).
proof: Proof. exact: gFid. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(fintype div bigop prime finset fingroup morphism) mathcomp(automorphism quotient commutator gproduct) mathcomp(gfunctor center gseries cyclic)