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Search: id:A083255
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| A083255 |
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Numbers n satisfying the following conditions: (i) cototient[n] > totient[n] or 2phi[n] < n; (ii) cototient[n]-totient[n] is an odd prime; (iii) n is an odd composite number. |
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+0
5
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| 165, 195, 5187, 5865, 7395, 10005, 15045, 16215, 21165, 22695, 27285, 37995, 42585, 44115, 50235, 57885, 59415, 60945, 64005, 310845, 346035, 347565, 486795, 635205, 707115, 890445, 979455, 994755, 1049835, 1070535, 1078815, 1083585, 1121745
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OFFSET
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1,1
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EXAMPLE
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Quite a number of terms are divisible by 3*5*17=255.
n=17425605=3.5.23.53.953:
cototient[m]=9712901>totient[m]=8712704,difference=197(prime)
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MATHEMATICA
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Do[s=EulerPhi[n]; c=n-s; If[Greater[c, s]&&PrimeQ[c-s]&&OddQ[c-s]&&!PrimeQ[n], Print[{n, c-s, n/255}]], {n, 1, 10000000}]
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CROSSREFS
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Cf. A000010, A051953, A036798, A067800, A083254.
Sequence in context: A105653 A038670 A035826 this_sequence A029563 A135806 A124409
Adjacent sequences: A083252 A083253 A083254 this_sequence A083256 A083257 A083258
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), May 08 2003
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