2, 3, 4, 4, 6, 8, 9, 12, 16

Pattern is : the series is the combination of three series -each term is twice the preceding term.
(i) 1^st, 4^st, 7^st term i. e 2,4,9,.......
(ii) 2^st, 5^st, 8^st term i, e 3,6,12.....
(iii) 3^st, 6^st, 9^st 4,8,16......
So, 9 is wrong.