proposition: Lemma eq_p'core pi rho G : pi =i rho -> 'O_pi^'(G) = 'O_rho^'(G).
proof: Proof. by move/eq_negn; apply: eq_pcore. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)