\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath}
\pagestyle{empty}
\begin{document}
\begin{equation*}
 \rho(\mathbf{R}_0,\mathbf{R}_0;\beta) = 
\int d\mathbf{R}_1 \dots d\mathbf{R}_{M-1} \ \rho(\mathbf{R}_0,\mathbf{R}_1;\tau)
\rho(\mathbf{R}_1,\mathbf{R}_2;\tau) \dots \rho(\mathbf{R}_{M-1},\mathbf{R}_0;\tau),
\end{equation*}
\end{document}