I can't find the nth power of a matrix

Question

i have the following matrix : $$A=\begin{equation*} \begin{pmatrix} 1 & -4 \\ 2 & -5 \\ \end{pmatrix} \end{equation*}$$ and i have to find $A^n$ . I calculated $A^2=\begin{equation*} \begin{pmatrix} -7 & 16 \\ -8 & 17 \\ \end{pmatrix} \end{equation*}$ , $A^3=\begin{equation*} \begin{pmatrix} 25 & -52 \\ 26 & -53 \\ \end{pmatrix} \end{equation*}$ , $A^4=\begin{equation*} \begin{pmatrix} -79 & 160 \\ -80 & 161 \\ \end{pmatrix} \end{equation*}$ However i cannot find a pattern between them . Can you help me ? Thank you .