There is also the Sabbath number, with the same principle, but it's the distance musicians are from the band Black Sabbath, as they changed formation countless

There is also the Sabbath number, with the same principle, but it's the distance musicians are from the band Black Sabbath, as they changed formation countless times. Together these three make up the Erdős Bacon Sabbath Number. Stephen Hawkin has the Erdős Bacon Sabbath Number of 8, one of the lowest known; he has the Erdős number of 4, Bacon number of 2 and Sabbath number of 2. Source: this book http://www.amazon.co.uk/pracht-van-priemgetallen-eeuwenlange-zoektocht/dp/9035138635/ http://www.amazon.co.uk/pracht-van-priemgetallen-eeuwenlange... (not an affiliate link) Edit: I didn't notice ColinWright's comment :)