Question. Assume that $\{p_n\}$ is the sequence of prime numbers, in increasing order. Does the series $$ \sum_{n=1}^\infty \frac{\sin p_n}{p_n} $$ converge?
The only criterion to establish convergence that I can think of, which might be of any use, is the Abel's Test, which requires that the partial sums of the sequence $b_n=\sin p_n$ are bounded, i.e., that there exists an $M>0$, such that $$ |\sin p_1+\cdots+\sin p_n|\le M, \quad\text{for all $n\in\mathbb N$}. $$
Any ideas?