\documentclass{article}
\usepackage[standard, thmmarks]{ntheorem}
\begin{document}
\begin{proof}
  There should be an endproof mark after the formula.
  \begin{displaymath}
    e^{i\pi}=-1
  \end{displaymath}
\end{proof}
There should be a theorem list below this line.
\listtheorems{proof}
\end{document}
