# How to write this math term?

I have the following sequence definition:

I can't find a way to write this in Latex. Any hints where to start?

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just use cases environment. search cases first. –  Leo Liu Nov 20 '11 at 17:32

Since the other cases questions ask some specific questions about it, here's a working example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
$g(n) = \begin{cases} \frac{2}{3}n & \text{wenn } n \equiv 0 \mod 3,\\ \frac{4}{3}n + \frac{1}{3} & \text{wenn } n \equiv 1 \mod 3,\\ \frac{4}{3}n - \frac{1}{3} & \text{wenn } n \equiv 2 \mod 3. \end{cases}$
\end{document}


The mathmode documentation is extremely helpful for answering these sorts of questions. You can find it on your system using texdoc or its equivalent.

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\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{equation*}
g(n) = \begin{cases}
\frac{2}{3} n &\ text{wenn } n \equiv 0 \mod 3 \\
\frac{4}{3} n - \frac{1}{3} & \text{ wenn } n \equiv 1 \mod 3 \\
\frac{4}{3} n + \frac{1}{3} & \text{ wenn } n \equiv 2 \mod 3
\end{cases}
\end{equation*}

\begin{equation*}
\def\arraystretch{1.3}%
g(n) = \left\{\begin{array}{llll}
\frac{2}{3} n & \text{wenn} & n \equiv 0 & \mod 3 \\
\frac{4}{3} n - \frac{1}{3} & \text{wenn} & n \equiv 1 & \mod 3 \\
\frac{4}{3} n + \frac{1}{3} & \text{wenn} & n \equiv 2 & \mod 3
\end{array}\right.
\end{equation*}

\end{document}

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The cases environment from amsmath is defined as \left\{\def\arraystretch{1.2}\begin{array}{@{}l@{\quad}l@{}} ... \end{array}\right.. –  Werner Nov 20 '11 at 17:54