Erdős Problem 307 #
Reference: erdosproblems.com/307
Are there two finite set of primes $P$ and $Q$ such that
$$ 1 = \left( \sum_{p \in P} \frac{1}{p} \right) \left( \sum_{q \in Q} \frac{1}{q} \right) $$ ?
Asked by Barbeau [Ba76].
[Ba76] Barbeau, E. J., Computer challenge corner: Problem 477: A brute force program.