求數列{(n+1)/2的n次幂}的前n項和

求數列{(n+1)/2的n次幂}的前n項和

Sn= 2/2+3/2^2+4/2^3+5/2^4+……+(n-1)/2^(n-2)+n/2^(n-1)+(n+1)/2^n(1)2Sn=2+3/2+4/2^2+5/2^3+……+(n-1)/2^(n-3)+n/2^(n-2)+(n+1)/2^(n-1)(2)(2)-(1)得Sn=2+1/2+1/2^2+1/2^3+……+1/2^(n-1)-(n+1)/2^n=1+[…