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3 <--the 1st term
3 + (-9) = -6 <--the 2nd term
-6 + (18) = 12 <--the 3rd term
12 + (-8) = 4 <--the 4th term
4 + (16) = 20 <--the 5th term
So using that pattern:
20 + (-7) = 13 <--the 6th trm
13 + (14) = 27 <--the 7th term
27 + (-6) = 21 <--the 8th term
21 + (12) = 33 <--the 9th term
...
Edwin
