This question examines the relationship between the general term and the first n terms of a series, the sum of the split terms, and the conversion method. It has a large amount of calculation and a certain degree of thinking difficulty, and belongs to a difficult problem. The answer is/exercise/math /804330, mainly because I was too lazy to do it, so I recited it directly.

Let the sum of the first n terms of the series {an} whose terms are all positive numbers be Sn and satisfy Sn? -(n？ +n-3)Sn-3(n？ +n)=0，n∈N*

(1) Find the value of a 1;

(2) Find the general term formula of sequence {an};

(3) It is proved that1/a1(a1+1)+1/A2 (A2+1)+... 1/3