One’s Erdos number is calculated as the minimum distance between oneself and Erdos using co-authorship to measure distance in the canonical manner. For example, at this moment, my Erdos number is at most 3. Here is a proof from the Journal of Graph Theory:

1. D. McQuillan and R.B. Richter, On 3-Regular Graphs Having Crossing Number at Least 2, Journal of Graph Theory 18 (8) (1994), pp. 831-839.

2. R.B. Richter and J. Siran, The Crossing number of K_{3,n} in a Surface, Journal of Graph Theory 21 (1996), pp. 51-54.

3. E. Bertram, P. Erdos, J. Siran, P. Horak, and Z. Tuza, Local and Global Average Degree in Graphs and Multigraphs, Journal of Graph Theory 18 (1994) 647-661.

There’s also the “Erdos number of the second kind” which restricts the eligibility of publications to those with only 2 authors. The 3rd publication above has more than 2 authors, and so it does not assist in calculating this number. Still I have an “Erdos number of the second kind” of at most 5. Here is a proof:

1. Dan McQuillan and R. Bruce Richter, Equality in a Result of Kleitman, J. Comb. Theory Ser. A 65(2) (1994), pp. 330-333.

2. Zhicheng Gao and R. Bruce Richter, 2-walks in Circuit Graphs, J. Comb. Theory Ser. B 62(2) (1994), pp. 259-267.

3. Zhicheng Gao and Nicholas Wormald, Sharp Concentration of the Number of Submaps in Random Planar Triangulations, Combinatorica 23(3) (2003), Pp. 467-486.

4. Laszlo A. Szekely and Nicholas Wormald, Bounds on the Measureable Chromatic Number of R^n, Discrete Mathematics 75(1- 3) (1989), pp. 343-372.

5. Paul Erdos and Laszlo A. Szekely, Counting Bichromatic Evolutionary Trees, Discrete Applied Mathematics 47(1) (1993), pp. 1-8.