4-digit integers: Squares of their digits

Take a random 4-digit integer (abcd),
then calculate a^2 + b^2 + c^2 + d^2

For example, 7283
then 7^2 + 2^2 + 8^2 + 3^2 = 126
Repeat the process
1^2 + 2^2 + 6^2 = 41
4^2 + 1^2 = 17
1^2 + 7^2 = 50
5^2 + 0^2 = 25
2^2 + 5^2 = 29
2^2 + 9^2 = 85
8^2 + 5^2 = 89
8^2 + 9^2 = 145

The sequence is 126, 41, 17, 50, 25, 29, 85, 89, 145

145 --> 1^2 + 4^2 + 5^2 = 42
42 ---> 4^2 + 2^2 = 20
20 ---> 2^2 + 0^2 = 4
4 ----> 4^2 = 16
16 ---> 1^2 + 6^2 = 37
37 ---> 3^2 + 7^2 = 58
58 ---> 5^2 + 8^2 = 89
89 ---> 8^2 + 9^2 = 145

It will either end in 1 or with 145