If $A \subseteq \{1, ..., N\}$ is a set with no $a, b, c \in A$ such that $a | (b+c)$ and $a < \min(b,c)$, then $|A| \le N/3 + O(1)$. This has been solved by Bedert [Be23].

If $A \subseteq \{1, ..., N\}$ is a set with no $a, b, c \in A$ such that $a | (b+c)$ and $a < \min(b,c)$, then $|A| \le N/3 + O(1)$. This has been solved by Bedert [Be23].

[Be23] Bedert, B., _On a problem of Erdős and Sárközy about sequences with no term dividing the sum of two larger terms_. arXiv:2301.07065 (2023).