list1 = [1642842, 780497, 1506284, 1438592, 1266530, 1154853, 965861, 
    610252, 1091847, 1209404, 1128111, 749998]
list2 = [(i, a, b, 1.0 * a / b) for i, (a, b) in enumerate(zip(list1, list1
    [1:]))]
for i, a, b, f in [i_a_b_f for i_a_b_f in list2 if i_a_b_f[3] > 1.5]:
    pass
Calculate factor difference between two list items