[apechai]

You get 2^n - 1 which is what he means by scaling 2^n. That's because the (sum of numbers 2^k for k = 0 to n - 1) = 2^n - 1.

Example: if you have one, she hires 2, those 2 hire 2 each. You have 1+2+4 = 7 = 8 - 1 = 2^3 - 1