305 repeating digits numbers

A repeating number carries a run of one digit: 0333, 5555, 7777. A run is easy to catch from a radio spot or the side of a passing truck, and easy to repeat to someone else later.

The longer the run and the closer it sits to the end, the rarer the number. Four of a kind at the end is the top of the range; three in a row in the middle is easier to find and still easy to say.