9, 1, 11, 5, 13, 19, ...
1st term = 9
2nd term = 1
3rd term = 11
4th term = 5
5th term = 13
6th term = 19
Look at the odd-numbered term:
1st term = 9
3rd term = 11
5th term = 13
...
That obvious goes 9,11,13,15,17,19,..., the odd numbers starting with 9.
Now look at the even numbered terms:
2nd term = 1
4th term = 5
6th term = 19
1+ 4=5
5+14=19
19+24=43
43+54=97
97+64=161
161+74=235
...
That obviously goes this way: start with 1, add 4, then add 10 more than 4, or 14.
the add 10 more than you added last time.
So the sequence goes like this:
9, 1, 11, 5, 13, 19, 15, 43, 17, 97, 19, 161, 21, 235, ...
Edwin