An unhappy number is a number that is not happy, i.e., a number
such that iterating this sum-of-squared-digits map starting with never reaches the number 1.
The first few unhappy numbers are 2, 3, 4, 5, 6, 8, 9, 11, 12, 14, 15, 16, 17, 18,
20, ... (OEIS A031177).
such that iterating this sum-of-squared-digits map starting with 
never reaches the number 1.
