Erdös Number

Erdös Number:
0: Erdös himself
1: direct collaborator with Erdös
2: collaborate with Erdös's collaborator
...
If you don't have a finite Erdös number, then your Erdös number is infinity.

Notes:
Einstein's Erdös Number is 2 through his assistant who worked with Erdös.

My Erdös Number is 4. My collaborator's lecturer whose professor worked with Erdös.