设S1=1＋1／1∧2+1/2∧2，S2=1+1/2∧2+1/3∧2，S3=1+1/3∧3+1/4∧

∵sn=1+[n^2+(n+1)^2]/[n²(n+1)²]=(n^2+n+1)^2/[n²(n+1)²] ∴√sn=（n^2+n+1)/[n(n+1)]=1+1/n-1/(n+1) ∴s=(1+1-1/2）+（1+1/2-1/3)+(1+1/3-1/4)+……+[1+1/n-1/(n+1)] =n+(1-1/2+1/2-1/3+1