1*2^4 + 1*2^3 + 0*2^2 + 1*2^1 + 1*2^0 + 1*2^(-1) + 0*2^(-2) + 1*2^(-3)
=16 + 8 + 0 + 2 + 1 + 1/2 + 0 + 1/8
=27 +0.5+0.125
27.625
2的n次方