This is a two-phase sequence.
Add a number - start with 7 and increase by 1 at each addition.
Subtract a number - start with 4 and decrease by 1 at each subtraction.
2 + 7 = 9
................9 - 4 = 5
5 + 8 = 13
...............13 - 3 = 10
10 + 9 = 19
...............19 - 2 = 17
17 + 10 = 27
...............27 - 1 = 26
2 5 9 10 13 17 19
2 9 5 13 10 19 17
that best completes the sequence 2 9 5 13 10 19 17 is 27.
18
The number after 17 is 27. 2+7 = 9 9 - 4 = 5 5 + 8 = 13 13 - 3 = 10 10 + 9 = 19 19 - 2 = 17 17 + 10 = 27
The next number in the sequence is 27.
twenty-seven.
27
27
27
One.
27