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A096887
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Initial values for f(x)=phi(sigma(x)) such that iteration of f ends in cycle of length=2.
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13
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4, 6, 7, 10, 11, 13, 17, 32, 36, 42, 48, 49, 50, 52, 54, 56, 57, 60, 62, 63, 64, 66, 67, 68, 69, 70, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 84, 85, 87, 88, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 110, 111, 112, 113, 114
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MATHEMATICA
| g[n_] := EulerPhi[ DivisorSigma[1, n]]; f[n_] := f[n] = Block[{lst = NestWhileList[g, n, UnsameQ, All ]}, -Subtract @@ Flatten[ Position[lst, lst[[ -1]]]]]; Select[ Range[115], f[ # ] == 2 &]
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CROSSREFS
| Cf. A000010, A000203, A095952, A095953, A096526, A095954, A096888, A096889, A096890, A095955, A095956.
Sequence in context: A153082 A026147 A032785 * A023631 A080641 A191920
Adjacent sequences: A096884 A096885 A096886 * A096888 A096889 A096890
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu) and Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 14 2004
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