% Display math.
\usepackage{amsmath}
\usepackage{mathtools}
\usepackage{amssymb}
\usepackage{ntheorem}

% New enviroment for remarks.
\theoremstyle{break}
\newtheorem{bem}{Bemerkung}

% New commands for math operators.
% Binomial coefficients.
\renewcommand{\binom}[2]{
  \biggl(
  \begin{matrix}
    #1 \\
    #2
  \end{matrix}
  \biggr)
}
% Euler numbers, first kind.
\newcommand{\eulerI}[2]{
  \biggl\langle
  \begin{matrix}
    #1 \\
    #2
  \end{matrix}
  \biggr\rangle
}
% Euler numbers, second kind.
\newcommand{\eulerII}[2]{
  \biggl\langle
  \negthinspace
  \biggl\langle
  \begin{matrix}
    #1 \\
    #2
  \end{matrix}
  \biggr\rangle
  \negthinspace
  \biggr\rangle
}
% Stirling numbers, first kind.
\newcommand{\stirlingI}[2]{
  \biggl[
  \begin{matrix}
    #1 \\
    #2
  \end{matrix}
  \biggr]
}
% Stirling numbers, second kind.
\newcommand{\stirlingII}[2]{
  \biggl\{
  \begin{matrix}
    #1 \\
    #2
  \end{matrix}
  \biggr\}
}