What do we know about the generating function of $\chi(n)$ (A010051) $$ f(x) = \sum_{n=0}^\infty \chi(n)x^n = \sum_{p\text{ prime}} x^p $$ for $\chi(n)$ the characteristic function of the primes:
$$ \chi(n) = \begin{cases} 1, & \text{if $n$ is prime}\\ 0, & \text{otherwise} \end{cases} $$ Are there some references I could take a look at?