Question

数学题..急急已知数列{an}的前n项和为Sn.对一切正整数n,点（Sn,n）都在函数f(x)㏒2（

Answer 1

n=log2(Sn+4)-2

log2(Sn+4)=n+2

Sn+4=2^(n+2)

Sn=4*2^n-4

S(n-1)=4*2^(n-1)-4

an=Sn-S(n-1)=4*2^n-4*2^(n-1)=2*2^n=2^(n+1)