De Bruijn sequence

A de Bruijn sequence is like a really long never-ending string of numbers. The way it works is that some number of numbers will show up again and again in this sequence. For example, if you use a de Bruijn sequence with 4 numbers, you might see something like 1234432112344321123443211... You'll keep seeing the same 4 numbers—12344321—over and over again in the same order. This repeating pattern makes a de Bruijn sequence really useful!