Paul Erdös (pron. AIR-dish), a Hungarian-American mathematician, was the most prolific mathematician of this century (~1500 papers), and collaborated with many people. His co-authors are said to have "Erdös number = 1", their co-authors' Erdös numbers are 2, and so on. Einstein and Kurt Gödel have Erdös # 1, while 7 is a high Erdös number for a professional mathematician.

My Erdös number has dropped to 4, because my co-author Dan Geer has written a soon-to-appear cryptography paper, "Threshhold Cryptography for the Masses," with the Israeli cryptographer Moti Yung, whose Erdös number is 2 (by way of Noga Alon). Dan's and Moti's paper will appear at the 2002 Financial Cryptography Conference.

Until early 2002, my Erdös number was 5, via the following route: My co-author Ross Ihaka is a statistician at U. Auckland. Ross' thesis adviser at UC Berkeley was David Brillinger. Brillinger's thesis adviser, in turn, was the Bell Labs statistician John Tukey, whose Erdös number was 2. It happens that Brillinger has published papers with both his adviser Tukey and his student Ihaka, so this co-authorship chain gives me an Erdös number of 5. Actually, since Tukey has 2 Erdös-1 coathors, and since Ihaka similarly has 2 Erdös-3 coathors, this gives me three 5-link paths to Erdös, reducing my number from 5 to 4 1/3.

I haven't found the paper-citations linking Tukey to Erdös, but here's the rest of the chain:

John W. Tukey's Erdös-1 coauthors were:
(See the Erdös Number Project's page, which lists all holders of Erdös #1 and Erdös #2.)

So, Tukey's Erdös # was 2.

Tukey's papers with Brillinger are:

D.R. Brillinger, L.V. Jones and J.W. Tukey, The Role of Statistics in Weather Resources Management, Vol. II, The Management of Weather Resources, Washington, Government Printing Office (1978).

D.R. Brillinger and J.W. Tukey, "Spectrum analysis in the presence of noise: some issues and examples," The Collected Works of J.W. Tukey, Vol. 2, (ed. D.R. Brillinger) Wadsworth (1985), pp. 1001-1141.

See (David Brillinger's publications #55 & #92.)

So, Brillinger's Erdös # is 3.

Now, Brillinger also has a statistics publication with his student, Ross Ihaka (my co-author):

Brillinger, D. R. and G. R. Ihaka (1982). ``Spectral estimation of seismic source parameters''. April Seismological Society of America Meeting, Anaheim California.

This proceedings volume is obscure and hard-to-find, unfortunately.

Anyway, Ross' Erdös # is 4, making mine 5.

Ross has another 4-link chain to Erdos:

From the Erdos number home page:

Erdos, P. ---- 1 ---> Mullin, Ronald C. ---- 2 ---> Lawless, Jerald F.

Lawless published with Ihaka's coauthor R. Gentleman, so Gentleman's number is 3, like Ihaka's adviser Brillinger's:

Gentleman, R. C., J. F. Lawless J. C. Lindsey and P. Yan (1994). "Multistate Markov models for analysing incomplete disease data with illustrations for HIV disease." Statistics in Medicine, 13, 805-821.

R. Ihaka and R. Gentleman (1996). "R: A language for data analysis and graphics,'" Journal of Computational and Graphical Statistics, 5, 299-314.

This paper is easier to find than Brillinger & Ihaka (82), but arguably is less purely mathematical than that paper.

- Don Davis (don @