In following question,a number series is given with one term missing. Choose the correct alternative
4 , 9 , 5 , 12 , 7 , 15 , 8 , x , 10.
8, 9, 8, 7, 10, 9, 6, 11, 10, , 12
5, 6, 9, 15, , 40
2 , 5 , 9 , 19 , 37 , x
In the Series 3, 9, 15, what will be the 21st term ?