Dihedral group:D18

Definition
The group is defined as the dihedral group of order math>18 and degree $$9$$. In other words, it has the presentation:

$$\langle a,x \mid a^9 = x^2 = e, xax = a^{-1} \rangle$$.

Other descriptions
The group can be constructed using GAP's DihedralGroup function:

DihedralGroup(18)