I know this is a hoax, but he cannot correctly describe it for a search.
What did he call when you can cover all dial combinations by entering numbers in sequence?
For example, consider a set of {1,2,3,4,5}, and I want to cover all 3-digit combinations with a minimum number of movements.
1,2,3,4,5,1,3,2 ... will cover {1,2,3}, {2,3,4}, {3,4,5}, {4, 5,1 }, {5,1,3}, {1,3,2}, etc.