calculus - Determining the sum of a series as a function of the variable x

I have the following series:
$$\sum_{n=0}^\infty (-1)^n \frac{x^{9n}}{n!}$$
I want to find the sum of the series of as a function of $x$.

It seems to resemble the Taylor series where of $e^x$ which is $\sum_{n=0}^{\infty} \frac{x^n}{n!}$.

I have also considered it as a telescoping series (which is not) and a geometric series ( which also does not seem to be the case).

How should I approach this problem ?