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A096990 Initial values for f(x)=sigma(phi(x))=A062402(x) such that iteration of f ends in cycle of length=3. 0
17, 19, 27, 29, 31, 32, 34, 35, 38, 39, 40, 41, 45, 47, 48, 52, 54, 55, 56, 58, 59, 60, 62, 69, 70, 72, 75, 78, 82, 84, 88, 90, 92, 94, 100, 110, 118, 132, 138, 150, 1057, 1117, 1153, 1201, 1237, 1241, 1261, 1271, 1301, 1313, 1321, 1333, 1349, 1351, 1359, 1381 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..56.

MATHEMATICA

f[n_] := DivisorSigma[1, EulerPhi[n]]; g[n_] := Block[{l = NestWhileList[f, n, UnsameQ, All]}, -Subtract @@ Flatten[ Position[l, l[[ -1]]]]]; Select[ Range[ 1396], g[ # ] == 3 &] (* Robert G. Wilson v, Jul 23 2004 *)

CROSSREFS

Cf. A062402, A095953.

Sequence in context: A281192 A073247 A133347 * A175384 A053689 A176462

Adjacent sequences:  A096987 A096988 A096989 * A096991 A096992 A096993

KEYWORD

nonn

AUTHOR

Labos Elemer, Jul 19 2004

EXTENSIONS

Edited and extended by Robert G. Wilson v, Jul 23 2004

STATUS

approved

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Last modified September 24 08:06 EDT 2021. Contains 347623 sequences. (Running on oeis4.)