What would be the rule for this pattern and the missing numbers? 12,_,18,33,_,39

Question

​number patter for numbers 12,?, 18,33,?,39

Answer 1

Not much to go on. Gap between 12 and 18 is 6 as is the gap between 33 and 39. The middle of the gaps are 15 and 36. 15+18=33 the start of the second sequence. So the missing numbers are 15 and 36.

Answer 2

It follows the rule number +15 then number -9. so the missing numbers are 27 and 24. the pattern is 12,27,18,33,24,39...