Runs of Consecutive Integers Having the Same Number of Divisors

Abstract

Our objective is to provide an upper bound for the length ${\ell }_N$ of the longest run of consecutive integers smaller than $N$ which have the same number of divisors. We prove in an elementary way that $\log {\ell }_N\ll (\log N\log \log N{)}^{\lambda }$, where $\lambda =1/2$. Using estimates for the Jacobsthal function, we then improve the result to $\lambda =1/3$.