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 A095954 Initial values for f(x)=phi(sigma(x)) such that iteration of f ends in a cycle of length 6. 12
 784, 800, 882, 912, 960, 972, 1008, 1024, 1050, 1072, 1080, 1089, 1104, 1168, 1204, 1216, 1225, 1232, 1248, 1250, 1264, 1281, 1290, 1296, 1302, 1308, 1332, 1350, 1352, 1360, 1368, 1371, 1372, 1392, 1400, 1407, 1416, 1425, 1440, 1456, 1461, 1464, 1467 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 EXAMPLE n=882:trajectory={882, 1296, 3300, [2880, 3024, 3840, 3456, 2560, 1800], 2880, ..} 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[1500], f[ # ] == 6 &] (* Robert G. Wilson v, Jul 14 2004 *) PROG (PARI) f(x)=eulerphi(sigma(x)) is(n)=my(t=f(n), h=f(t)); while(t!=h, t=f(t); h=f(f(h))); h=f(h); t!=h && t!=(h=f(h)) && t!=(h=f(h)) && t==f(f(f(h))) \\ Charles R Greathouse IV, Nov 23 2013 CROSSREFS Cf. A000010, A000203, A095952, A096887, A095953, A096526, A096888, A096889, A096890, A095955, A095956. Sequence in context: A158399 A007243 A146978 * A351476 A257355 A187935 Adjacent sequences:  A095951 A095952 A095953 * A095955 A095956 A095957 KEYWORD nonn AUTHOR Labos Elemer, Jul 13 2004 STATUS approved

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Last modified May 16 11:35 EDT 2022. Contains 353704 sequences. (Running on oeis4.)