proposition: Lemma ucn_subS n G : 'Z_n(G) \subset 'Z_n.+1(G).
proof: Proof. by rewrite -{1}['Z_n(G)]ker_coset morphpreS ?sub1G. 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)