answer:
-f(n+1) = f(n) x 2
-on the 10th day you'd receive $512
-this function works by taking the output of the last input and multiplying it by 2 to find the new output.
-i'd rather take 40 days of this money scheme.
example of use:
f(10) = f(9) x 2
output of f(9) is 256 so f(10) = 256 x 2