My excellent sister-in-law-in-law Virginia Transue, widow of a mathematician who was the son of a mathematician, mused on Facebook this morning about the extraordinarily prolific and collaborative Hungarian mathematician Paul Erdös:
Paul Erdös collaborated with so many people that mathematicians are often asked what their ERDÖS NUMBER is. If you wrote a paper with him your number was 1. If you wrote a paper with somebody who had written one with him it was 2… My Bill’s Erdös number was 2, his father’s was 3
From my 7/27/09 Language Log posting “Erdös?”:
There are linguists with Erdős numbers of 2 (András Kornai), 3 (Geoff Pullum, via András), and 4 (me, via Geoff)



