Erdős number

Paul Erdős (1913-1996) was an influential and very productive mathematician. He published more than 1,500 papers during his life.

Considering this enormous scientific output, most scientists will have published with someone who has published with someone etc. who finally published together with Paul Erdős. Friends of Paul Erdős humorously suggested to measure this "collaborative distance" between a scientist and Erdős and called this measure Erdős number.

My Erdős number is (at most) 4.

Here's how it's calculated:

1. I coauthored with Jürgen Jost: Elze et al. (2011)
2. Jürgen Jost coauthored with Shing-Tung Yau: Jost and Yau (1983)
3. Shing-Tung Yau coauthored with Ronald L. Graham: Chung et al. (1996)
4. Ronald L. Graham coauthored with Paul Erdős: Erdős and Graham (1972)