## Not all the semigroups \PGL(2, 7) are idempotent generated. ## ## GAP log file gap> n:=8;; G:=PrimitiveGroup(8,5);; a:=Transformation( [ 6, 2, 3, 4, 6, 6, 6, 6 ] );; gap> gens:=List(GeneratorsOfGroup(G), x-> AsTransformation(x, n));; gap> S:=Semigroup(Concatenation(gens, [a]));; gap> Size(S); 108984 gap> I:=Idempotents(S, 4);; gap> T:=Semigroup(I); gap> Size(T)=Size(S)-Size(G); false