\begin{equation}
\begin{aligned}
& \left\{\begin{matrix}j_1 & j_2 & j_3\\ j_4 & j_5 & j_6\end{matrix}\right\} = \sum_{m_1, \dots, m_6} (-1)^{\sum_{k= 1}^6 (j_k - m_k)} \begin{pmatrix}j_1 & j_2 & j_3\\ -m_1 & -m_2 & -m_3\end{pmatrix} \times\\
& \begin{pmatrix}j_1 & j_5 & j_6\\ m_1 & -m_5 & m_6\end{pmatrix}
\begin{pmatrix}j_4 & j_2 & j_6\\ m_4 & m_2 & -m_6\end{pmatrix}
\begin{pmatrix}j_4 & j_5 & j_3\\ -m_4 & m_5 & m_3\end{pmatrix}
\end{aligned} \end{equation}