The numbers are not illegal to have for other purpose, but only if you're using them to construct (or act as) the actual work of art, or to break other rules.

The numbers are not illegal to have for other purpose, but only if you're using them to construct (or act as) the actual work of art, or to break other rules. In all the cases that were presented, there was malice in the actions involved, by intending to circumvent rules by pretending it was something else, rather than honestly happening on the equivalent number.