\documentclass[12pt]{article}
\usepackage{geometry}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[yscale=0.7]
\draw (0,0) rectangle (7,3) (3,3) -- (3,0) -- (0,3)
(0.2,0.2) node[above right,font=\Huge]{$0$}
foreach \X [count=\Y] in {1,3,7} {(0,3.5-\Y) node[red,left] {$\X$}
(-0.5+\Y,3) node[red,above] {$\X$}}
foreach \X [count=\Y] in {2,4,5,6} {(2.5+\Y,3) node[above] {$\X$}};
\end{tikzpicture}
\end{document}
As for the code in your comment:
\documentclass[12pt]{article}
\usepackage{geometry}
\usepackage{mathtools}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[yscale=0.7]
\draw (0,0) rectangle (6,3) (3,3) -- (3,0) -- (0,3)
(0.4,0.4) node[above right,font=\Huge]{$\mathbf 0$}
foreach \X/\Z [count=\Y] in {i_1,\cdots/\vdotswithin{i_1},i_k} {(0,3.5-\Y)
node[red,left] {$\Z$}
(-0.5+\Y,3) node[red,above] {$\X$}}
foreach \X [count=\Y] in
{i_{k+1},\cdots,i_N} {(2.5+\Y,3) node[above] {$\X$}};
\end{tikzpicture}
\end{document}