%% 
%%  Ein Beispiel der DANTE-Edition
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%%  2. Auflage
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%%  Beispiel 09-08-33 auf Seite 462.
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%%  Copyright (C) 2016 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.
%% 
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%% ==== 
% Show page(s) 1
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{145.16928pt}
\AtBeginDocument{\setlength\parindent{0pt}}
%StartShownPreambleCommands
\usepackage{mathtools}
%StopShownPreambleCommands
\begin{document}
\[ x = \sum_{1\le i\le j\le n}x_{ij} \]
\[ x = \sum_{\mathclap{1\le i\le j\le n}}x_{ij} \]
\end{document}