Study the pattern and complete the series : 15, 31, 63, 127, 255, ?

Answer 1

It follows the logic below:
15 x 2 = 30 + 1 = 31
31 x 2 = 62 + 1 = 63
63 x 2 = 126 + 1 = 127
127x 2 = 254 + 1 = 255
255x 2 = 510 + 1 = 511

The answer is 511

Answer 2

The series contains ((2^n)-1) terms starting with n=4.
So the required term will have n=9 => 512 -1 = 511.

Answer 3

511 will complete the series as indicated below:

The pattern shows that the numbers are doubled with a "1" added in.
Starting with 15x2 = 30 + 1 = 31. And ending with 255x2 = 510 +1 = 511.

Answer 4

each consecutive number is add up with 16,32,64,128,.....

31-15=16
63-31 =32

127-63 =64

255-127=128

.....-255=256 so value is (256+255=511)