Sort-Then-Add Sequence
The sequence produced by sorting the digits of a number and adding them to the previous number. The values starting with
, 2, ... are
2, 4, 6, 8, 10, 12, 14, 16, 18, 11, 22, 24, ... (OEIS A070196).
If the sorting-then-adding algorithm is applied iteratively until a sorted number is obtained, then for
, 2, ..., the
algorithm terminates on 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 11, 12, 13, 14, 15, 16, 17,
18, 19, 22, 33, ... (OEIS A033862). The first
few numbers not known to terminate are 316, 452, 697, 1376, 2743, 5090, ... (OEIS
A033861). The least numbers of sort-then-add
persistence
, 2, ..., are 1, 10, 65, 64, 175, 98,
240, 325, 302, 387, 198, 180, 550, ... (OEIS A033863).

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