In this sequence there are actually two sequences. 1 sequence for the numerators and one sequence for the denominators. The following transformation applies to the sequence for the denominators : +9
This creates the following sequence: [2, 11, 20, 29, 38, 47, 56]
The following transformation applies to the sequence for the numerators: -6
This creates the following sequence: [10, 4, -2, -8, -14, -20, -26]
Take a good look at how to rewrite the fractions in the series to recognize the pattern.
For example, 1/5 can be rewritten as 2/10