##### Explanation :

In this problem the given series follows the following pattern of (11 + 4n)^{2} where n = 0, 1, 2, 3, ... i.e.

1st term = (11 + 4 x 0)^{2} = 11^{2} = 121

2nd term = (11 + 4 x 1)^{2} = 15^{2} = 225

3rd term = (11 + 4 x 2)^{2} = 19^{2} = 361

4th term = (11 + 4 x 3)^{2} = **(23)**^{2 }= 529

So, the missing term is 529.