Equation 18.47.68DAD90BE35BE

\begin{equation} \frac{c^2}{9m}\mathrm e^{(a^2+b^2)/(2m)} \leq A_ m(a,b)\leq \frac{2\pi }{9m}\mathrm e^{(a^2+b^2)/(2m)}. \end{equation}