A124177 Consider the map f that sends m to m + (sum of even digits of m) - (sum of odd digits of m). Sequence gives numbers m such that f^(k)(m) = m for some k.
0, 22, 26, 27, 34, 35, 44, 49, 52, 63, 66, 78, 79, 81, 88, 99, 104, 107, 108, 112, 115, 121, 126, 133, 134, 143, 144, 151, 156, 165, 178, 187, 211, 224, 229, 232, 233, 283, 290, 314, 336, 341, 358, 363, 385, 413, 431, 467, 470, 489, 492, 516, 538, 561, 583, 615
Offset: 1
Examples
26 and 27 loop on themselves, but 28 doesn't. 26 -> 34 -> 35 -> 27 -> 22 -> 26 27 -> 22 -> 26 -> 34 -> 35 -> 27 28 -> 38 -> 43 -> 44 -> 52 -> 49 -> 44.
Links
- Eric Angelini, Table of n, a(n) for n = 1..182
- Eric Angelini, Self-loopers.
Programs
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PARI
is(n,S=List())={until(setsearch(Set(S),n=A304440(n)),listput(S,n));n==S[1]} \\ M. F. Hasler, May 18 2018
Comments