What is the sequence to 2 9 5 13 10 19 17?

Answer 1

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