Erdos Number 2

"Paul Erdos, the late widely-traveled and incredibly prolific Hungarian mathematician of the highest caliber, wrote hundreds of mathematical research papers in many different areas, many in collaboration with others. His Erdos number is 0. His co-authors have Erdos number 1. People other than Erdos who have written a joint paper with someone with Erdos number 1 but not with Erdos have Erdos number 2, and so on. If there is no chain of co-authorships connecting someone with Erdos, then that person's Erdos number is said to be infinite." This is quoted from the The Erdos Number Project, which is currently the official keeper of all Erdos Numbers.

In 1980, Alan J. Hoffman co-authored with Erdos, and therefore aquired Erdos Number 1. ( Erdos Number 1 List .) In 1993, Alan Hoffman, Peter Brucker and myself wrote the paper Series Parallel Composition of Greedy Linear Programming Problems (Mathematical Programming, 62, 1993, 1-14,) which gave both of us Erdos Number 2. ( Erdos Number 2 List .) Since Erdos passed away in 1996, Erdos number 2 is the optimal number one can obtain from here on.