\documentclass[12pt]{article}
\usepackage{tikz}
\usetikzlibrary{arrows}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\begin{document}
\begin{tikzpicture}
%\node (name) at position {lable}; 
\node (00) at (0,0) {$\dots$};
\node (20) at (2,0) {$A_{n+2}$};
\node (40) at (4,0) {$A_{n+1}$};

\node(22) at (2,2) {0};
\node(42) at (4,2) {0};

\node(31) at (3,1) {$C_{n+1}$};

\draw[->,thick] (00) -- (20);
\draw[->,thick] (20) --(40);
\draw[->,thick] (20) --(31);
\draw[->,thick] (22) --(31);
\draw[->,thick] (31) --(42);
\draw[->,thick] (31) --(40);
\end{tikzpicture}
\end{document}