（当n趋向于无穷大时有解）an=（n+1）^2+1/(n+1)^2-1a1=2^2+1/2^2-1a2=3^2+1/3^2-1……a1+a2+a3+……an=2^2+3^2+4^2……+(n+1)^2+1/2^2+1/3^2+……1/(n+1)^2-n=n(n+1)(2n+1)/6-1+π^2/6-1-n=n(n+1)(2n+1)/6+π^2/6-n-2
