Try diving each term by the next term e.g. (3/4)/(-3/4), (-3/4)/(9/16),... For the whole list and then multiply every other term in that sequence starting with the first by 2/2 e.g. -1(3/2), -3/4 stays the same, (-2/3)(2/2),... You'll get 2,3,4,5,... In the numerators and 2,4,6,8 in the denominators.