can you show me some coin ? i don't really understand about X11 X13 or X15
Go to coinwarz.com an filter coins by algorithm (X11, X13 etc.)
There are plenty of coins that it would be not possible to list them here for you.
To start, DarkCoin (DRK) was the first X11 coin and might still be one of the best X11 coins to mine.
Explore more options on coinwarz.