It is well-known that A: The series of the reciprocals of the primes diverges My question is whether property A is in some sense a truth strongly tied to the nature of the prime numbers. For instance, can you give an example of an infinite subset $A \subseteq \mathbb{N}$ (different from $P$) such that $\sum_{a \in A} \frac{1}{a}$ diverges, $A$ contains infinitely many prime numbers and the $k$-th member of $A$ is greater than the $k$-th prime for infinitely many $k$? Property A tells us that the primes are a rather *fat* subset of $\mathbb{N}$. Is there a way to define a topology on $\mathbb{N}$ such that every dense subset of $\mathbb{N}$ (under this topology) corresponds to a *fat* subset of the natural numbers? What do you think about this?