§ The chromatic polynomial (TODO)
I've been on a combinatorics binge lately, so I'm collecting cool facts about
the chromatic polynomial. We first define the chromatic function of a graph,
which is a generating function:
f[G](x)≡number of ways to color G with x colors⋅xn
If we have a single vertex K1, then f[K1](x)=nxn, since we can color
the single vertex with the n colors we have.
§ Composition of chromatic funcions of smaller graphs
§ The chromatic function is a polynomial