Integers with small digits in multiple bases

Abstract

We show that, for any $r\ge 1$, if $g_1,\dots ,g_r$ are distinct coprime integers, sufficiently large depending only on $r$, then for any $\hat{I}\mu >0$ there are infinitely many integers $n$ such that all but $\hat{I}\mu \log n$ of the digits of $n$ are $\le g_i/2$ in base $g_i$ for all $1\le i\le r$. In other words, for any fixed large bases, there are infinitely many $n$ such that almost all of the digits of $n$ are small in all bases simultaneously. This is both a quantitative and qualitative improvement over previous work of Croot, Mousavi, and Schmidt. As a consequence, we obtain a weak answer to a conjecture of Graham concerning divisibility of $\left(\genfrac{}{}{0ex}{}{2n}{n}\right)$.

23 pages