How to graph the antiderivative of Weierstrass function: $f(x)= \sum\limits_{k=0}^ \infty \frac{\cos\left(13^k\pi x \right)}{2^k}$.

Question

The Weierstrass function: $f(x)= \sum\limits_{k=0}^ \infty a^k {\cos\left(b^k\pi x \right)}$ where $0<a<1, \ b \in 2\mathbb{N}-1, \ ab > 1+\frac{3\pi}{2}$ is an example of a continuous function that has a derivative at no point.

Let $f(x):= \sum\limits_{k=0}^ \infty \frac{\cos\left(13^k\pi x \right)}{2^k}$ is a Weierstrass function and it is contentious so it had an an antiderivative i.e $F(x):=\int_0^x f(t)dt$

I am curious how the graph of this $F$ looks like because $F(x)$ is differentiable at all $x \in \mathbb{R}$ but it doesn't have a second derivative at any point.

I don't know how to graph such functions or what tools to use.