proposition: Lemma centS A B : B \subset A -> 'C(A) \subset 'C(B).
proof: Proof. by move=> sAB; rewrite centsC (subset_trans sAB) 1?centsC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)