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 n'' to yield n^, , , , etc., a single-digit number, known as the digital root of n, is eventually obtained. The digital roots of the first few integers are 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, ... (OEIS A010888).

196-algorithm | additive persistence | digit | digital root | Kaprekar number | multiplicative persistence | narcissistic number | recurring digital invariant