Erdős Problem 38 #
Reference: erdosproblems.com/38
Does there exist $B \subset \mathbb{N}$ which is not an additive basis, but is such that for every set $A \subseteq \mathbb{N}$ of Schnirelmann density $\alpha$ and every $N$ there exists $b \in B$ such that [ \lvert (A \cup (A+b)) \cap {1, \ldots, N} \rvert \geq (\alpha + f(\alpha)) N ] where $f(\alpha) > 0$ for $0 < \alpha < 1$?