It is easy to get the Chromatic-Polynomial of a Circulant-Graph of size $n$ with one parameter $P[C_{n}(i),x]$. Is there a way to get an explicit formula for the chromatic polynomial of a circulant graph with two parameters? I am particularly interested in the asymptotic behavior of the expression
$$\frac{P[C_{n}(i,j),n]}{n^n} - \frac{P[C_{n}(i),n]*P[C_{n}(j),n]}{n^{2n}}$$
as $ n\rightarrow\infty$.