A) 513
B) 511
C) 523
D) 517
The logic of this series is: The next number would be double of current number plus 1
Example: The next number of 15 would be (15 x2) + 1 i.e. 31
The next number would be (31x 2) + 1 i.e. 63. And so on ….
Hence answer is: (255×2) + 1 i.e. 511