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 : -2
This creates the following sequence: [-5, -7, -9, -11, -13, -15]
The following transformation applies to the sequence for the numerators: -7
This creates the following sequence: [3, -4, -11, -18, -25, -32]
Take a good look at how to rewrite the fractions in the series to recognize the pattern.
For example, 7/4 can be rewritten as -7/-4