[vog]

Note that you can optimize this by removing the "(1-c)^n" part, because its absolute value is smaller than 0.5 for big n, so it can't influence the (rounded) result.

This trick is especially funny when performed using a hand calculator. For instance, just calculate the powers of the golden ratio and observe numbers like "xxxxx,0000yyy" "xxxxx,9999yyy", which become closer and closer to integers.