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Search: id:A036798
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| A036798 |
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Odd n such that there exists an even number k < n with phi(k) = phi(n). |
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9
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| 105, 165, 195, 315, 495, 525, 585, 735, 825, 945, 975, 1155, 1365, 1485, 1575, 1755, 1785, 1815, 1995, 2145, 2205, 2415, 2475, 2535, 2625, 2805, 2835, 2925, 3003, 3045, 3135, 3255, 3315, 3465, 3675, 3705, 3795, 3885, 3927, 4095, 4125, 4305, 4389, 4455
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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These numbers m appear to satisfy cototient[m] > totient[m] or 2phi[m] < m; - they seem to be the missing terms mentioned in A067800. - Labos E. (labos(AT)ana.sote.hu), May 08 2003
All elements in this sequence must have 2*phi(n) < n, but not the reverse. See A118700. - Frank Adams-Watters (FrankTAW(AT)Netscape.net), May 21 2006
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MATHEMATICA
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Select[ Range[1, 4483, 2], Mod[ #, EulerPhi[ # ]] != # - EulerPhi[ # ] &] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 10 2004)
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CROSSREFS
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Cf. A067800, A083254.
Cf. A091495 (Odd, squarefree n such that n/phi(n) > 2).
Cf A118700, A119434.
Sequence in context: A118678 A152940 A076762 this_sequence A119434 A091495 A046405
Adjacent sequences: A036795 A036796 A036797 this_sequence A036799 A036800 A036801
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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