Paul Erdős was a Hungarian mathematician who wrote many papers in diverse fields of mathematics. Coauthors of Erdős are said to have an "Erdos number" 1; those who collaborated with them hold an Erdős number 2, and so on. Erdős himself has an Erdős number 0. The graph shows the collaborations between authors with Erdős number 1, ordered according to authors with the highest number of collaborations. Point the mouse at the vertices to see the name of the mathematicians (an asterisk after the name means the mathematician is deceased).