\documentclass{article}% Heiko Oberdiek

\input{binhex}
\makeatletter
\def\Hexnumber#1{\expandafter\@Hexnumber\csname c@#1\endcsname}
\def\@Hexnumber#1{\hex{#1}}
\makeatother

\usepackage{enumerate}

\begin{document}

\begin{enumerate}[\Hexnumber{enumi}.]\addtocounter{enumi}{10}
\item eleven
\item twelve
\item thirteen
\item forteen
\item fifteen
\item sixteen
\end{enumerate}

\end{document}