A033862 Sorted number reached from starter n in Sort-then-add sequence, or -1 if never reaches sorted number.

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 11, 12, 13, 14, 15, 16, 17, 18, 19, 22, 33, 22, 23, 24, 25, 26, 27, 28, 29, 33, 44, 55, 33, 34, 35, 36, 37, 38, 39, 44, 55, 66, 77, 44, 45, 46, 47, 48, 49, 55, 66, 77, 88, 99, 55, 56, 57, 58, 59, 66, 77, 88, 99, 233, 233, 66, 67, 68, 69, 77, 88

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base

Comments

Probably a(316) = -1.

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..315
• Eric Weisstein's World of Mathematics, Sort-then-Add Sequence.

Programs

Python

from itertools import islice
def a(n):
    while n != (s:=int("".join(sorted(str(n))))): n += s
    return s
print([a(n) for n in range(1, 72)]) # Michael S. Branicky, Jan 15 2024