What is the next number in the sequemce

Question

3, -6, 12, 4, 20 ?

Answer 1

One possibility would be 13.  There may be other sequences which will fit as well.

 

I will write below a table of first differences where there seems to be a pattern.

 

3    -6    12    4    20

 

  -9    +18  -8  +16

 

If the next difference were -7, the next number would be 13 and the term after that 27.