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A096526
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Initial values for f(x)=phi(sigma(x)) such that iteration of f ends in cycle of length=4.
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9
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324, 400, 484, 490, 530, 544, 576, 630, 660, 672, 684, 690, 714, 722, 750, 756, 768, 770, 772, 777, 780, 792, 804, 810, 819, 828, 832, 833, 840, 841, 846, 852, 858, 864, 868, 870, 872, 876, 888, 892, 901, 906, 910, 918, 920, 924, 930, 936, 940, 948, 952
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| n=324: trajectory=324, 660, [576, 1512, 1280, 864], 576, ...}
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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[1000], f[ # ] == 4 &] (from Robert G. Wilson v Jul 14 2004)
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CROSSREFS
| Cf. A000010, A000203, A095952, A096887, A095953, A095954, A096888, A096889, A096890, A095955, A095956.
Sequence in context: A088214 A117550 A045287 * A111278 A014792 A202094
Adjacent sequences: A096523 A096524 A096525 * A096527 A096528 A096529
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Jul 13 2004
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