that A equals
$\displaystyle \left[\begin{matrix}0&2&0\\0&0&2\\0&0&0\\0&0&0\end{matri x}\left|\begin{matrix}-1\\0\\2\\0\end{matrix}\right]$
To find $\displaystyle A^n$ you can firstly need to diagonalise $\displaystyle A$ for an example look here.
Diagonalization