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Search: id:A096998
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| A096998 |
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Consider iteration of the function f(x)=sigma(phi(x))=A062402(x). Sequence gives numbers n such that the trajectory of n returns to n. |
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| 1, 3, 7, 12, 15, 28, 31, 60, 72, 124, 168, 195, 252, 255, 744, 1240, 1512, 1651, 2418, 2520, 3066, 3844, 4092, 4800, 5080, 5376, 6045, 6138, 6552, 9906, 9920, 10200, 12264, 20440, 30855, 36792, 46228, 58968, 60984, 65535, 67963, 81880, 122640
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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96 => 63 => 91 => 195 => 252 => 195 => ..., therefore 195 and 252 are in the sequence.
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MATHEMATICA
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a = {}; f[n_] := DivisorSigma[1, EulerPhi[ n]]; Do[ AppendTo[ a, NestWhileList[f, n, UnsameQ, All][[ -1]]]; a = Union[a], {n, 10^6}]; Take[ a, 43] (from Robert G. Wilson v Jul 21 2004)
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CROSSREFS
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Cf. A062402, A096850.
Sequence in context: A107790 A075895 A033015 this_sequence A122981 A122982 A101589
Adjacent sequences: A096995 A096996 A096997 this_sequence A096999 A097000 A097001
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jul 19 2004
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EXTENSIONS
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Edited, corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 21 2004
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