The omission is that it's simply recursive. You might add the digits up to 36, whose digits then add up to 9. Simply reapply to the sum if the sum has more th

The omission is that it's simply recursive. You might add the digits up to 36, whose digits then add up to 9. Simply reapply to the sum if the sum has more than 1 digit, and you'll still arrive at 9.