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A091847
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Perfect totient numbers, omitting powers of 3.
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3
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15, 39, 111, 183, 255, 327, 363, 471, 2199, 3063, 4359, 4375, 5571, 8751, 15723, 36759, 46791, 65535, 140103, 208191, 441027, 4190263, 9056583, 57395631, 172186887, 236923383, 918330183, 3932935775, 4294967295, 4764161215
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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.
Douglas E. Iannucci, Deng Moujie and Graeme L. Cohen, On Perfect Totient Numbers, J. Integer Seqs., Vol. 6, 2003.
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MATHEMATICA
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fQ[n_] := !IntegerQ@ Log[3, n] && Plus @@ FixedPointList[ EulerPhi@# &, n] == 2n + 1 (* Robert G. Wilson v, Nov 06 2010 *)
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CROSSREFS
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A082897 has more information.
Sequence in context: A186295 A259429 A126950 * A062222 A325659 A223432
Adjacent sequences: A091844 A091845 A091846 * A091848 A091849 A091850
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Mar 13 2004
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STATUS
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approved
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