Verified answer

3, 7, 19, 55

..4..12..36

The ratio of your geometric series is 36/12 = 3

S0 a_5 = a_4 +3(36) = 55 +108 = 163

a_6 = a_5 +3(108) = 163 +324= 487

a_7 = a_6 + 3(324) = 487 +972 = 1459

3 to 7 is seperated by 4, 7 to 19 is seprated by 12, and 19 to 55 is seperated by 36. So the next number would be 36times3 +55.

the first increase was 4 and it multiplies by 3 every time. So first one you add 4, then 12, then 36, 108, 324, 972. The next 3 numbers would be these:

163, 487, 1459.