Cantor's Transfinite Numbers (1874), Menger Sponge (1926), and Fractals (1975). And from Wikipedia (yawn):   In  mathematics , a  Ford circle  is a  circle  with  centre  at ( p/q , 1/(2 q  2 )) and  radius  1/(2 q  2 ), where p/q  is an  irreducible fraction , i.e.  p  and  q  are