We have the following sum:
$$\displaystyle \sum_{n=4}^\infty \dfrac{(-1)^n}{\log(\log(n))} $$
I have a hunch this series is conditionally convergent, but I get nowhere using the ratio test. What test would be best to apply to this particular series?
You may just use the alternating series test:
the function $x \mapsto \dfrac{1}{\log(\log(x))}$ is decreasing,
as $x \to \infty$, you have $\dfrac{1}{\log(\log(x))} \to 0.$