Sloane's Gap. Mathematical and Social Factors Explain the Distribution   of Numbers in the OEIS
  The Online Encyclopedia of Integer Sequences (OEIS) is made up of thousands of numerical sequences considered particularly interesting by some mathematicians. The graphic representation of the frequency with which a number n as a function of n appears in that database shows that the underlying function decreases fast, and that the points are distributed in a cloud, seemingly split into two by a clear zone that will be referred to here as "Sloane's Gap". The decrease and general form are explained by mathematics, but an explanation of the gap requires further considerations. 
Nicolas Gauvrit, Jean-Paul Delahaye, Hector Zenil
math.PR