题干
已知数列{an}的前n项和为Sn，且满足a1=1，nSn+1﹣（n+1）Sn=
，n∈N*
| n |
| ( |
| n |
| + |
| 1 |
| ) |
| 2 |
| n |
| ( |
| n |
| + |
| 1 |
| ) |
| 2 |
