proposition: Lemma partG_eq1 pi G : (#|G|`_pi == 1%N) = pi^'.-group G.
proof: Proof. exact: partn_eq1 (cardG_gt0 G). 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)