Question 1153678

<pre>
3, -6, 12, 4, 20, ?

Pattern seems to be 3-9 = -6, -6+18 = 12, 12-8 = 4, 4+16 = 20, ...

So the additions are, starting with 3:  -9, +18, -8, +16, next is -7 (?) 

The continuation I see is  20-7 = 13