Infinitely many composites n with n+1 dividing σ(n+1)
Determine whether there exist infinitely many positive composite integers n such that n+1 divides σ(n+1), where σ(·) denotes the sum-of-divisors function.
References
Open question 1: Are there infinitely many positive composite integers $n$ such that $n+1\mid \sigma(n+1)$?
— Divisibility and Sequence Properties of $σ^+$ and $\varphi^+$
(2508.11660 - Mandal, 6 Aug 2025) in Section 2, Main Results (Open question 1)