Digitaddition -- from Wolfram MathWorld

Start with an integer n, known as the digitaddition generator. Add the sum of the digitaddition generator's digits to obtain the digitaddition n^'. A number can have more than one digitaddition generator. If a number has no digitaddition generator, it is called a self number. The sum of all numbers in a digitaddition series is given by the last term minus the first plus the sum of the digits of the last. If the digitaddition process is performed on n^' to yield its digitaddition n^(''), on...