%% 
%%  A DANTE-Edition example
%% 
%%  Example 02-04-2 on page 39.
%% 
%%  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[]{article}
\pagestyle{empty}
\setlength\textwidth{129.70511pt}
\setlength\parskip{10pt}
\AtBeginDocument{\setbox0\hbox{$ $}}

\usepackage{blkarray}

\begin{document}
\begin{blockarray}{c|c|c}
11 & 21 & 31\\
\begin{block}{>{\itshape}c\BAmulticolumn{2}{>{\itshape}r}}
12 & 23--32\\ 13 & 23--33\\
\end{block}
14 & 24 & 34
\end{blockarray}
\end{document}