Absolute stability region
Stable region in red.

Coefficients

\begin{align} \begin{array}{c|ccc} - \frac{\sqrt{15}}{10} + \frac{1}{2} & \frac{5}{36} & - \frac{\sqrt{15}}{15} + \frac{2}{9} & - \frac{\sqrt{15}}{30} + \frac{5}{36}\\ \frac{1}{2} & \frac{5}{36} + \frac{\sqrt{15}}{24} & \frac{2}{9} & - \frac{\sqrt{15}}{24} + \frac{5}{36}\\ \frac{\sqrt{15}}{10} + \frac{1}{2} & \frac{\sqrt{15}}{30} + \frac{5}{36} & \frac{2}{9} + \frac{\sqrt{15}}{15} & \frac{5}{36}\\ \hline & \frac{5}{18} & \frac{4}{9} & \frac{5}{18} \end{array}\end{align}

Properties