High Quality Content by WIKIPEDIA articles! A happy number is defined by the following process. Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers or sad numbers. More formally, given a number n = n0, define a sequence n1, n2, ... where ni + 1 is the sum of the squares of the digits of ni. Then n is happy if and only if there exists i such that ni = 1. If a number is happy, then all members of its sequence are happy; if a number is unhappy, all members of its sequence are unhappy.

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