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Search: id:A095953
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| A095953 |
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Initial values for f[x]=phi[sigma(x)] such that iteration of f ends in cycle of length=3. |
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+0
13
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| 16, 18, 21, 24, 25, 27, 28, 30, 31, 33, 34, 35, 37, 38, 39, 40, 44, 45, 46, 47, 51, 53, 55, 58, 59, 61, 65, 71, 83, 86, 89, 109, 131, 137, 149, 900, 1116, 1152, 1156, 1200, 1236, 1260, 1300, 1320, 1380, 1386, 1410, 1428, 1458, 1488, 1500, 1518, 1524, 1533, 1536
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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n=900: trajectory={900, 2160, 1920, [1536, 1200, 1860], 1536, ...}
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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[1540], f[ # ] == 3 &] (from Robert G. Wilson v Jul 14 2004)
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CROSSREFS
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Cf. A000010, A000203, A095952, A096887, A096526, A095954, A096888, A096889, A096890, A095955, A095956.
Sequence in context: A043705 A031315 A077914 this_sequence A084800 A065426 A031168
Adjacent sequences: A095950 A095951 A095952 this_sequence A095954 A095955 A095956
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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 13 2004
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 14 2004
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