Well this is long one's long.
1. an = 15 +6n (adding 6 each time)
2. an = an-1 + 2n(adding +2 +4 +6)
3. an = a0 *-2n (multiplying -2 each time)
4. an= an-1 +16/n (adding +16 +8 +4 +2)
5.
you can continue, 1,1,2,3 (fibonacci sequence)
or you can continue 1, 1, 2, 8(multiplying 1x 2x 4x)
6.
you can continue, 48,49,50,51 (just adding one)
or you can continue 48,49,50,49(increasing then decreasing back)
7.
you can continue, A,B,C.. Y,Z,AZ(like excel)
or you can continue A,B,C.. Y,Z,A(loop)
8. just divide 8 times
