TomDihedral( m )
TomDihedral
constructs the table of marks of the dihedral group of
order m. For each divisor d of m, a dihedral group of order m =
2n contains subgroups of order d according to the following rule. If
d is odd and divides n then there is only one cyclic subgroup of
order d. If d is even and divides n then there are a cyclic
subgroup of order d and two classes of dihedral subgroups of order d
which are cyclic, too, in the case d = 2, see example below).
Otherwise, (i.e. if d does not divide n, there is just one class of
dihedral subgroups of order d.
gap> d12 := TomDihedral( 12 ); rec( name := [ "1", "2", "D_{2}a", "D_{2}b", "3", "D_{4}", "6", "D_{6}a", "D_{6}b", "D_{12}" ], subs := [ [ 1 ], [ 1, 2 ], [ 1, 3 ], [ 1, 4 ], [ 1, 5 ], [ 1, 2, 3, 4, 6 ], [ 1, 2, 5, 7 ], [ 1, 3, 5, 8 ], [ 1, 4, 5, 9 ], [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] ], marks := [ [ 12 ], [ 6, 6 ], [ 6, 2 ], [ 6, 2 ], [ 4, 4 ], [ 3, 3, 1, 1, 1 ], [ 2, 2, 2, 2 ], [ 2, 2, 2, 2 ], [ 2, 2, 2, 2 ], [ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ] ] ) gap> DisplayTom( d12 ); 1: 12 2: 6 6 3: 6 . 2 4: 6 . . 2 5: 4 . . . 4 6: 3 3 1 1 . 1 7: 2 2 . . 2 . 2 8: 2 . 2 . 2 . . 2 9: 2 . . 2 2 . . . 2 10: 1 1 1 1 1 1 1 1 1 1
GAP 3.4.4