Hello everyone

Forgive me if I am excluding information of some sort. My english mathematical repetoire isn't too impressive and I don't know any discrete math basics.

Anyway I asked my math teacher how to form the following problem into an simple formula. He said that we're talking discrete math when encountering problems of this sort, and he wouldn't rather sit and do discrete math early in the morning.

My problem was this.

We got a base of $\displaystyle 20$, and a growth of $\displaystyle \frac {base} {5}$. This number must be a simple number, such as 4 in this case. Any decimals will be ignored (and the number rounded down, example: $\displaystyle 5.5 = 5$)

The next step is the new base $\displaystyle 20 + \frac {20}{5}$ divided by 5 again.

$\displaystyle \frac { 20 + 4 } { 5 }$

Is there a way to come up with a formula for expressing the result of $\displaystyle N$ times we do this operation?

I am currently absolutely uninitiated into discrete math, so keep the talk simple and explanatory, please.

Thanks for all replies