2^1 - 1 = 1
2^2 -1 = 2
2^3 -1 = 4
2^4 - 1 = 8
2^5 -1 = 16
2^6 -1 = 32
2^7 - 1 = 64
2^8 -1 = 128
Sum = 1 + 2 +4 + 8 + 16 + 32 +64 + 128 = 255
Answer is B
