McKay correspondence

The simply laced Dynkin diagrams come in two infinite families:

A_n, with n dots:

D_n, with n dots:

Beware: the Dynkin diagram A_n, with n dots, corresponds to the subgroup ℤ_n+1 ⊂ SO(3), the symmetry group of an (n+1)-gonal pyramid. The Dynkin diagram D_n, with n dots, corresponds to the subgroup D_n-2 ⊂ SO(3), the symmetry group of an (n-2)-gonal prism. The pictures above reflect these facts.

I created the Dynkin diagrams here. I hereby release them into the public domain.