or
according to Linda

2 to the power of (n-1) and
therefore

2^(32-1)
= $
2,147,483,648

and Eric says

Linda's math
is correct, but
she is figuring the number cents.

The answer
is $21,474,836.49

and
Tim
says

Your
solution to
the horseshoe puzzle is wrong.

It's not 2^(n-1) (i.e.2^31) but 2^n - 1 (i.e. 2^32 - 1).

So the answer should be $42,949,672.95

If you don't believe me consider the case for four nails.

The farmer charges:

# Amount

1 $0.01

2 $0.02

3 $0.04

4 $0.08

-------

$0.15 <- i.e. $0.01 x 2^4 - 1