Extremal orders of compositions of certain arithmetical functions

József Sándor, László Tóth

We study the exact extremal orders of compositions $f(g(n))$ of certain arithmetical functions, including the functions $\sigma (n)$, $\varphi (n)$, ${\sigma }^{\ast }(n)$ and ${\varphi }^{\ast }(n)$, representing the sum…