Mean square of the error term in the asymmetric many dimensional divisor problem

Let $ba=(a_1,a_2,ldots,a_k)$, where $a_j (j=1,ldots,k)$ are positive integers such that $a_1 leq a_2 leq cdots leq a_k$. Let $d(ba;n)=sum_{n_1^{a_1}cdots n_k^{a_k}=n}1$ and $Delta(ba;x)$ be the error term of the summatory function of $d(ba;n)$. In this paper we show an asymptotic formula of the mean square of $Delta(ba;x)$ under a certain condition. Furthermore, in the cases $k=2$ and 3, we give unconditional asymptotic formulas for these mean squares.

On the Tong-type identity and the mean square of the error term for an extended Selberg class

In 1956, Tong established an asymptotic formula for the mean square of the error term in the summatory function of the Piltz divisor function $d_3(n).$ The aim of this paper is to generalize Tongs method to a class of Dirichlet series that satisfy a functional equation. As an application, we can establish the asymptotic formulas for the mean square of the error terms for a class of functions in the well-known Selberg class. The Tong-type identity and formula established in this paper can be viewed as an analogue of the well-known Voronois formula.