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A096890
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Initial values for f(x)=phi(sigma(x)) such that iteration of f ends in cycle of length=18.
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13
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401408, 414050, 436032, 455625, 462400, 466608, 476100, 486300, 486900, 512337, 522242, 526974, 543600, 544644, 544944, 546192, 546861, 554304, 559504, 571536, 572313, 575028, 577200, 579856, 583200, 585528, 599694, 604300, 609429, 611618
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..30.
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MATHEMATICA
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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[624900], f[ # ] == 18 &]
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CROSSREFS
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Cf. A000010, A000203, A095952, A096887, A095953, A096526, A095954, A096888, A096889, A095955, A095956.
Sequence in context: A209910 A190837 A205094 * A157826 A215998 A186606
Adjacent sequences: A096887 A096888 A096889 * A096891 A096892 A096893
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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) and Robert G. Wilson v, Jul 14 2004
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STATUS
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approved
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