Erdös Number

One of the most prolific authors of all time in mathematics, including many areas of mathematics useful to computer science, was the late Paul Erdös. Erdös coauthored so many papers with other mathematicians (see the Erdös Number Project) that there arose the notion of one's Erdös number, defined recursively as follows: Your Erdös number is

• 0 if you are Erdös;

• n+1 if you have coauthored with someone whose Erdös number is n but not with someone whose Erdös number is less than n.

• undefined, otherwise.

Thus, e.g., your Erdös number is 1 if you coauthored with Erdös; 2 if you coauthored with a coauthor of Erdös but not with Erdös himself, etc.

As far as I can tell, my Erdös number is 4 - not real impressive. I trace this to my coauthorship with Russ Miller (who has Erdös number 3), who coauthored with both Quentin Stout and Susanne Hambrusch, each of whom is listed at the Erdös Number Project among those with Erdös number 2.