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 A356548 Let S(n)=sigma(n)/3. Numbers k such that S^m(k)=k, 1/3-sociable numbers (of any order). 0
 120, 672, 7560, 7680, 8064, 8184, 8840, 9600, 10540, 34944, 36576, 38080, 65520, 71680, 75264, 77748, 90272, 472416, 510720, 523776, 605024, 654080, 1100190, 1124352, 14913024, 16149760, 27797760, 33931072, 34012160, 459818240 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS It appears that, for initial i=660880440, the sequence x->S(x) diverges. Barring such cases, the next 3 terms would be 775898880, 874897408 and 1476304896. LINKS Table of n, a(n) for n=1..30. EXAMPLE 120 -> 120 so 120 is a term, a 3-perfect number. 7680 -> 8184 -> 7680, a group of 2 sociable terms. 7560 -> 9600 -> 10540 -> 8064 -> 8840 -> 7560, a group of 5 sociable terms. 34944 -> 38080 -> 36576 -> 34944, a group of 3 sociable terms. CROSSREFS Subsequences: A005820 (3-perfect), A113546 (1/3-sociable numbers of order 1 and 2). Sequence in context: A342923 A292365 A306373 * A113546 A281771 A166069 Adjacent sequences: A356545 A356546 A356547 * A356549 A356550 A356551 KEYWORD nonn,more AUTHOR Michel Marcus, Aug 11 2022 STATUS approved

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Last modified July 23 10:25 EDT 2024. Contains 374547 sequences. (Running on oeis4.)