Let $\tan \alpha , \tan \beta$ and $\tan \gamma ; \alpha , \beta , \gamma \neq \frac { ( 2 n - 1 ) \pi } { 2 } , n \in N$ be the slopes of the three line segments $O A , O B$ and $O C$, respectively, where $O$ is origin. If circumcentre of $\Delta A B C$ coincides with origin and its orthocentre lies on $y$-axis, then the value of $\left( \frac { \cos 3 \alpha + \cos 3 \beta + \cos 3 \gamma } { \cos \alpha \cdot \cos \beta \cdot \cos \gamma } \right) ^ { 2 }$ is equal to: