Erdős Problems

Tags Prizes

OPEN

Let $\sigma_1(n)=\sigma(n)$, the sum of divisors function, and $\sigma_k(n)=\sigma(\sigma_{k-1}(n))$. Is it true that \[\lim_{k\to \infty} \sigma_k(n)^{1/k}=\infty?\]

#410: [ErGr80]

number theory, iterated functions