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A067800
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Nonprime n such that phi(n) > n/2.
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4
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1, 9, 15, 21, 25, 27, 33, 35, 39, 45, 49, 51, 55, 57, 63, 65, 69, 75, 77, 81, 85, 87, 91, 93, 95, 99, 111, 115, 117, 119, 121, 123, 125, 129, 133, 135, 141, 143, 145, 147, 153, 155, 159, 161, 169, 171, 175, 177, 183, 185, 187, 189, 201, 203, 205, 207, 209, 213, 215
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OFFSET
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1,2
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COMMENTS
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Sequence is similar to A014076(n) giving odd nonprimes. Only 3 terms = 105, 165, 195 are not in the sequence among 59 terms < 210.
Cototient[m] > totient[m] equivalent to 2phi[m] < m; the missing terms mentioned here seem to form A036798. - Labos Elemer, May 08 2003
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LINKS
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MATHEMATICA
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Select[Range[250], !PrimeQ[#]&&EulerPhi[#]>#/2&] (* Harvey P. Dale, Aug 29 2021 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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