Let $A:=\{n \in \mathbb N : \sigma(n) \text{ is a perfect square}\}$ . I can show that $A$ is infinite . Let $A(n):=|A \cap [1,n]|$ . What can we say about $\liminf A(n)/n$ and $\limsup A(n)/n$ ?
2026-03-28 03:27:43.1774668463
Upper and lower density of the set of natural numbers whose sum of positive divisors is a perfect square
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