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+\documentclass[12pt]{article}
+
+\begin{document}
+
+$$
+   E_{\rm tot}({\bf R}_1 \ldots {\bf R}_N) = NE_{\rm vol}(\Omega ) 
+   + \frac{1}{2} \sum _{i,j} \mbox{}^\prime \ v_2(ij;\Omega ) 
+   + \frac{1}{6} \sum _{i,j,k} \mbox{}^\prime \ v_3(ijk;\Omega ) 
+   + \frac{1}{24} \sum _{i,j,k,l} \mbox{}^\prime \ v_4(ijkl;\Omega )
+$$
+
+\end{document}