 This is done by means of the Erdős number, which is 0 for Paul Erdős himself, 1 for someone who co-wrote an article with him, 2 for someone who co-wrote with someone who co-wrote with him, etc.People have combined the Bacon number and the Erdős number to form the Erdős–Bacon number, which is the sum of the two.Kevin formed a band called The Bacon Brothers with his brother, Michael.