%% 
%%  An UIT Edition example
%% 
%%  Example 08-03-4 on page 161.
%% 
%%  Copyright (C) 2010 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{177.70511pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\StartShownPreambleCommands

\StopShownPreambleCommands
\begin{document}
$a\atopwithdelims() b$       \medskip

${n \atopwithdelims() k} =
 {n!\above1pt k!(n-k)!}$     \medskip

$\displaystyle{a\atopwithdelims\{. b}$
\end{document}