You only need to bother calculating the series for 1/(4 - z)^2 (why?).

Did you bother to read the link I gave in my reply here: http://www.mathhelpforum.com/math-he...er-series.html

Now look for the pattern in where n = 0, 1, 2, 3, ....

If you need more help, please say where you are stuck.