2, 4, 8, 16, ...

-3, -1, 3, 9, ...

23, 21, 19, 17, ...

8, 5, 0, -7, ...

2, 5, 8, 11, ...

-6, -3, 0, 3, ...

-2, -5, -8, -11, ...

-11, -8, -5, -2, ...

22, 64

22, 44

32, 44

32, 64

 $a_n=2n+1$  

 $a_n=4n-1$  

 $a_n=4^n-1$  

 $a_n=2^n+1$  

2, 3, 4, 5, ...     ; $a_n=2n$  

3, 5, 7, 9, ...     ; $a_n=2n+1$  

1, 3, 9, 27, ...    ; $a_n=3^n$  

2, 4, 8, 16, ...     ; $a_n=2^{n-1}$  

-3, -7, -11, -15, ...

5, 4, 3, 2, ...

1, 2, 4, 8, ...

2, 4, 6, 8, ...

-100, -80, -60, ...

-25, -8, 9, ...

2, 12, 22, ...

43, 62, 81, ...

-11

-14

-17

-20

9, 5, 1, -3, ...

0, -2, -4, -6, ...

20, 13, 6, -1, ...

7, 4, 1, -2, ...