Happy Number Definition

A happy number is defined by the following process: Start with any positive integer $I$ , the replace $I$ by the sum of the squares of its digits in base-ten. Repeat the process until $I$ either equals $1$ (where it will stay at $1$ forever), or it loops endlessly in a cycle that does not include $1$ . Those numbers for which this process ends in $1$ are happy numbers, while those that never get $1$ are unhappy numbers (or sad numbers).