\documentclass{article}
\usepackage{array}

\begin{document}

\begin{equation}
 \left[ \begin{array}{*{2}{c}|c}
          1 & 2  & 4  \\
          5 & 6  & 8  \\
          9 &  10    &  12 \\
 \end{array} \right]
\end{equation}

\end{document}
