The next number in the sequence is 27.
11
11
11.
It is 129.
27.
The next figure would be 21, followed by 11 & 10.
22
The next number in the sequence is 27.
18
37.
It's, 7n+6
This is a peculiar number sequence which follows the following rule: +7, -4, +8, -3, +9, -2... The next few functions would be +10, -1, +11, -0 And thus the next few numbers in the sequence would be 17+10=27, 27-1=26, and so on. The sequence in total goes 2, 9, 5, 13, 10, 19, 17, 27, 26, 37, 37.
20
119. un = (-n4 + 15n3 - 77n2 + 225n + 192)/6
The next number is 27. Nice puzzle! The reason is on discussion page, for those who are still working on it.
22