Explicit expression of a Barban & Vehov Theorem

Abstract

We prove that $$ S=\sum_{n \leq N} {(\sum\limits_{d|n}\lambda_d^{(1)})^2}/{n}\leq 166 \frac{\log N}{\log z} $$ where $N \geq z \geq 100$, where the $\lambda_d^{(1)} $ is the weight introduced by Barban & Vehov in 1968, namely $$ \lambda_d^{(1)}= \begin{cases} \mu(d) & \text{when $d \leq z$} ,\\ \mu(d)\frac{\log({z^2}/{d})}{\log z} & \text{when $z< d \leq z^2$}, \\ 0 & \text{when $z^2<d$,} \end{cases} $$ where $\mu$ is the Möbius function.