On an open problem of Skiba

Zhenfeng Wu, Chi Zhang, Wenbin Guo

Let $\sigma =\{{\sigma }_i|i\in I\}$ be some partition of the set $\mathbb{P}$ of all primes, that is, $\mathbb{P}={\bigcup }_{i\in I}{\sigma }_i$ and ${\sigma }_i\cap {\sigma }_j=\varnothing$ for all $i\ne j$. Let…