1.1,5,13,25...n2.3,9,18,30.n

1.1,5,13,25...n2.3,9,18,30.n
1.1,5,13,25...n
2.3,9,18,30.n

1.1,5,13,25...n2.3,9,18,30.n
1、an=2n^2-2 n
2、an=(3n^2+3n-6)/2 n=2

1. 依次加4，8，12……
2. 依次加6，9，12……

N（N+4）
3N（N+1）/2

第一题是41
第二题是45

an=2n^2-2 n
2、an=(3n^2+3n-6)/2 n=2
第一题是41
第二题是45