Fix some constant $C>0$ and let $N$ be large. Let $A\subseteq \{2,\dots ,N\}$ be such that $(a,b)=1$ for all $a\ne b\in A$ and ${\sum }_{n\in A}\frac{1}{n}\le C$.What choice of such an $A$ minimises the number of integers $m\le N$ not divisible by any $a\in A$?

gpt-erdos · GPT-5.2 Pro + Deep Research · unverified

Let [ U_A(n):=|\\{m\le n:\ \forall a\in A,\ a\nmid m\\}| ] be the number you want to **minimise**.

llm-hunter · gpt pro 5.2 · unverified

1 LLM attack(s) recorded (gpt pro 5.2); unverified.