It was something I read in an issue of Discover many many years ago. They were talking about a system of representing numbers that could represent both finite and infinite numbers. The system was composed entirely of up and down arrows and a means of indicating infinite repeating. They stated that a single infinite up is omega, the largest integer, and that an up followed by a single infinite down is iota, its reciprocol. The system could actually count beyond these.

http://discovermagazine.com/1995/dec...typlusonea599/

Edit:

The notation is messed up in the online version...