1.记第n个正方形的边长是a[n]
{a[1]=2,
{a[n]=2^(1/2)*a[n-1],n>=2
为等比数列
a[n]=2*(2^(1/2))^(n-1)
a[5]=8
2.记第n个正方形的面积为s[n]=a[n]^2=2^(n+1)
sum(1,5,s[n])=121