Special Session 100: Roots and trends in number theory

On a sum involving the sum-of-divisors function
Feng Zhao
North China University of Water Resources and Electric Power
Peoples Rep of China
Co-Author(s):    Jie Wu
Abstract:
Let $\sigma(n)$ be the sum of all divisors of $n$ and let $[t]$ be the integral part of $t$. In this paper, we shall prove that $$ \sum_{n\le x} \sigma\Big(\Big[\frac{x}{n}\Big]\Big) = \frac{\pi^2}{6} x\log x + O(x(\log x)^{2/3}(\log_2x)^{4/3}) $$ for $x\to\infty$, and that the error term of this asymptotic formula is $\Omega(x)$.