Does anyone know about this series? Looks like it converges depending on the value of $a$. Do you know any closed form solution to find the $a$ that makes the series become zero. $$\sum_{n=1}^\infty \frac{\cos( a \ln(n))}{\sqrt n}$$
2026-03-26 21:35:01.1774560901
series with the term $\cos(\ln(x))$
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