It is known that the sum of the first n terms of the arithmetic sequence an is Sn, Sn = n ^ 2, sum 1 / (A1A2) + 1 / (a2a3) +. + 1 / [(an-1an] (n ≥ 2) The teacher said, use the split term elimination method to find the complete process,

It is known that the sum of the first n terms of the arithmetic sequence an is Sn, Sn = n ^ 2, sum 1 / (A1A2) + 1 / (a2a3) +. + 1 / [(an-1an] (n ≥ 2) The teacher said, use the split term elimination method to find the complete process,

When n = 1, A1 = S1 = 1 & # 178; = 1n ≥ 2, an = SN-S (n-1) = n & # 178; - (n-1) & # 178; = 2n-1n = 1, A1 = 2-1 = 1. The general formula satisfying the general formula sequence {an} is an = 2n-11 / [ana (n + 1)] = 1 / [(2n-1) (2n + 1)] = (1 / 2) [1 / (2n-1) - 1 / (2n + 1)] 1 / (A1A2) + 1 / (a2a3) +... + 1