((2n-1)*2^n+1)/2^n
=[(2n-1)*2^n]/2^n+1/2^n
=(2n-1) + (1/2)^n
则
Sn = [1+(2n-1)]*(2n-1)/2 + 1/2*[1-(1/2)^n]/(1-1/2)
=n*(2n-1) + [1-(1/2)^n]