what is the next number?2,3,5,9,

问题描述:

what is the next number?2,3,5,9,

17.....................
3=2*2-1 5=3*2-1 9=5*2-1 n=(n-1)*2-1

17

2*2-1=3
3*2-1=5
5*2-1=9
9*2-1=17
以此类推
ok?