proposition: Lemma centY A B : 'C(A <*> B) = 'C(A) :&: 'C(B).
proof: Proof. by rewrite cent_gen centU. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)