Can you explain the top number (2^4 + 4 - 1)? I understand the bottom number 4 is probably because you're choosing 4 values out of the set of numbers from the t

Can you explain the top number (2^4 + 4 - 1)? I understand the bottom number 4 is probably because you're choosing 4 values out of the set of numbers from the top, but not sure how you got 2^4 + 4 - 1.