Author: Lotertius
There is website, HAD2KNOW.COM (if you have the interest, you can go and check it out), reporting the following information:
They use the method of splitting any number into its[……]
Happy Numbers and Unhappy Numbers (1)
(中文) 快樂數字與不快樂數字（二）
(中文) 快樂數字與不快樂數字（三）
