Population math help!

I'm trying to figure out a reasonable population for my colony of Santa
Maria, and I'm finding that I've forgotten all that high school math...

Population growth is a compound-interest type equation, I think, but
damned
if I can remember the actual formula. So, given:

Initial population of X
Average annual growth of Y%
Average annual immigration of Z
and
Years Since Colony Established of Q

there must be an easier way of doing this than repeating (X x Y) + Z
a number of times equal to Q. (I'm positing a 97-year old colony. You
can
understand my desire to find an easier way.) You can't just do
q{(xy)+z}, because (xy) is a constantly increasing number.

Please help...

Embarrasingly inumerate,

Brian (burger00@camosun.bc.ca)
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