What is the next number in the series?15, 31, 63, 127, 255, ?

The next number in the series is 511.

Here's the step-by-step explanation:

This series is based on the pattern of doubling the previous number and adding 1.

1. Start with 15, double it to get 30, then add 1 to get 31.
2. Double 31 to get 62, then add 1 to get 63.
3. Double 63 to get 126, then add 1 to get 127.
4. Double 127 to get 254, then add 1 to get 255.
5. So, to find the next number, double 255 to get 510, then add 1 to get 511.

The next number in the series is 511.

Here's the step-by-step explanation:

This series is based on powers of 2, minus 1.

1. 2^1 - 1 = 1
2. 2^2 - 1 = 3
3. 2^3 - 1 = 7
4. 2^4 - 1 = 15
5. 2^5 - 1 = 31
6. 2^6 - 1 = 63
7. 2^7 - 1 = 127
8. 2^8 - 1 = 255
9. 2^9 - 1 = 511

So, the next number in the series is 511.