proposition: Lemma ucn_central n G : 'Z_n.+1(G) / 'Z_n(G) = 'Z(G / 'Z_n(G)).
proof: Proof. by rewrite ucnSn cosetpreK. 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)