proposition: Lemma cent_gen A : 'C(<<A>>) = 'C(A).
proof: Proof. by apply/setP=> x; rewrite -!sub1set centsC gen_subG centsC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)