- The 13th Discworld novel and a standalone, although it uses some characters and locations from Pyramids and its events influence later works.
- Illegal number (Wikipedia)
An illegal number is a number that represents information which is illegal to possess, utter, propagate, or otherwise transmit in some legal jurisdiction. Any piece of digital information is representable as a number; consequently, if communicating a specific set of information is illegal in some way, then the number may be illegal as well.