## Not all the semigroups \PSL(2, 8) are idempotent generated. ## ## GAP log file gap> n:=9;; G:=PrimitiveGroup(9,8);; a:=Transformation( [ 1, 2, 3, 5, 4, 5, 4, 4, 5 ] );; gap> gens:=List(GeneratorsOfGroup(G), x-> AsTransformation(x, n));; gap> S:=Semigroup(Concatenation(gens, [a]));; gap> Size(S); 4655169 gap> I:=Idempotents(S, 5);; gap> T:=Semigroup(I); gap> Size(T)=Size(S)-Size(G); false