數列3/2,9/4,13/4,65/16.的前n項和為___

數列3/2,9/4,13/4,65/16.的前n項和為___

3/2=1+1/2
9/4=2+1/4
13/4=3+1/4
65/16=4+1/16
.
An=n+2^(-n)
Sn=(1+2+…+n)+(1/2+1/4+1/8+1/16+…+1/2^n)
=(1+n)*n/2+(1-2^(-n))