Erdős number
A low Erdős number is a status symbol among 20th century mathematicians and is similar to the 6degreesofseparation concept.
Let $e(p)$ be the Erdős number of person $p$. Your Erdős number is

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0 if you are Paul Erdős

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$\mathrm{min}\{e(x)x\in X\}+1$, where $X$ is the set of all persons you have authored a paper with.
Title  Erdős number 

Canonical name  ErdHosNumber 
Date of creation  20130322 13:10:55 
Last modified on  20130322 13:10:55 
Owner  mathcam (2727) 
Last modified by  mathcam (2727) 
Numerical id  12 
Author  mathcam (2727) 
Entry type  Definition 
Classification  msc 01A60 
Related topic  ErdHosNumber 