In each of these questions a number series is given. In each series only one number is wrong. Find out the wrong number.

1.5, 9, 51, 205, 616, 1233, 1234

Correct option is E

Wrong number = 9
Pattern of the series:
1.5×6+1= 10
10×5+1=51
51×4+1=205
205×3+1=616
616×2+1=1233
1233×1+1=1234