Taxicab number
A taxicab number is the name given by mathematicians to a sequence of special numbers: 2, 1729 etc.  A taxicab number is the smallest number that can be expressed as the sum of two positive cubes in n distinct ways.  It has nothing to do with taxis, but the name comes from a well-known conversation that took place between two famous mathematicians: Godfrey Hardy and Srinivasa Ramanujan.