Periodic points of the Sum of squares of digits Function:
0, 1, 4, 16, 20, 37, 42, 58, 89, 145
Example
7 -> 49 -> 97 -> 140 -> 17 -> 50 -> 25 -> 29 -> 85 -> 89 -> 145 -> 42 -> 20
And
20 -> 4 -> 16 -> 37 -> 58 -> 89 -> ... -> 20
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