Upper Bounds on Integer Complexity

Abstract

Define $||n||$ to be the \emph{complexity} of $n$, which is the smallest number of $1$s needed to write $n$ using an arbitrary combination of addition and multiplication. John Selfridge showed that $||n|| \geq 3\log_3 n$ for all $n$. Richard Guy noted the trivial upper bound that $||n|| \leq 3\log_2 n$ for all $n>1$ by writing $n$ in base 2. An upper bound for almost all $n$ was provided by Juan Arias de Reyna and Jan Van de Lune. This paper provides the first non-trivial upper bound for all $n$. In particular, for all $n>1$ we have $||n|| \leq A \log n$ where $A = \frac{41}{\log 55296}$.