proposition: Lemma indexg1 G : #|G : 1| = #|G|.
proof: Proof. by rewrite -divgS ?sub1G // cards1 divn1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)