18
29, assuming it is an algebraically reclusive sequence.
Well, darling, it looks like we're playing the guessing game. The next number is 15. How did I figure that out, you ask? Well, I just added the differences between each number and found the pattern. Easy peasy lemon squeezy.
The pattern rule is: 4 5 6 7 8 and so the next number will be 33+9 = 42
18-the correct number should be 20.
The next number in the series 4, 12, 6, 12, 36, 18, 36
The next number in the series 4-12-6-12-36-18-36.. is 108.
18
108
108
108
24
26
108
24
30!
The number 7 comes next.