(\sqrt{5}-\sqrt{15})^{361}=
\sum_{k=0}^{361}
\begin{pmatrix}
361\\
k
\end{pmatrix}
5^{\frac{361-k}{2}}15^{\frac{k}{2}}=
\sum_{k=0}^{361}
\begin{pmatrix}
361\\
k
\end{pmatrix}
(5^{361-k+k}3^{k})^{\frac{1}{2}}=
5^{361}
\sum_{k=0}^{361}
\begin{pmatrix}
361\\
k
\end{pmatrix}
3^{\frac{k}{2}}=
5^{361}361!\sum_{k=0}^{361}\frac{3^{\frac{k}{2}}}{k!(361-k)!}