https://www.impan.pl/en/publishing-house/journals-and-series/colloquium-mathematicum/all/103/1/87562/nonaliquots-and-robbins-numbers
Nonaliquots and Robbins numbersAll
Let $\varphi(\cdot)$ and $\sigma(\cdot)$ denote the Euler function and the sum of divisors function, respectively. We give a lower bound for the number of...
robbins