gap> G:=DihedralGroup(IsPermGroup,6);
Group([ (1,2,3), (2,3) ])
gap> Ge:=AsList(G);
[ (), (2,3), (1,2), (1,2,3), (1,3,2), (1,3) ]
gap> PrintArray(MultiplicationTable(Ge));
[ [  1,  2,  3,  4,  5,  6 ],
  [  2,  1,  4,  3,  6,  5 ],
  [  3,  5,  1,  6,  2,  4 ],
  [  4,  6,  2,  5,  1,  3 ],
  [  5,  3,  6,  1,  4,  2 ],
  [  6,  4,  5,  2,  3,  1 ] ]
gap> Size(G);
6
gap> GeneratorsOfGroup(G);
[ (1,2,3), (2,3) ]
gap> IsCyclic(G);
false
gap> IsAbelian(G);
false
gap> IsSimpleGroup(G);
false
gap> Centre(G);
Group(())
gap> Aut:=AutomorphismGroup(G);
<group of size 6 with 2 generators>
gap> StructureDescription(Aut);
"S3"
gap> H:=Group((2,3));
Group([ (2,3) ])
gap> IsSubgroup(G,H);
true
gap> IsNormal(G,H);
false
gap> N:=Subgroup(G,[Ge[4],Ge[5]]);
Group([ (1,2,3), (1,3,2) ])
gap> Elements(N);
[ (), (1,2,3), (1,3,2) ]
gap> IsNormal(G,N);
true
gap> List(RightCosets(G,N),Elements);
[ [ (), (1,2,3), (1,3,2) ], [ (2,3), (1,2), (1,3) ] ]
gap> StructureDescription(FactorGroup(G,N));
"C2"
gap>