Need maffs help, where should I look for if I'm interested in functions in which the value is derived from the value before it? For instance:

f(n) = f(n-1) + f(n-1)^2

Is there even a way to convert these into "regular" functions? I'm mostly concerned with n€Z situations, but I guess I can ask the question for N as well.

If anyone could point me to the right direction / discipline, I'd be very grateful!