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Search: id:A079310
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| A079310 |
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Numbers n such that (6*phi(n)-1,6*phi(n)+1) is a twin prime pair, where phi is Eulers' totient function (A000010). |
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| 1, 2, 3, 4, 6, 11, 13, 19, 21, 22, 26, 27, 28, 31, 36, 38, 41, 42, 51, 53, 54, 55, 59, 62, 64, 68, 71, 73, 75, 80, 82, 88, 91, 95, 96, 100, 101, 102, 106, 110, 111, 117, 118, 120, 121, 125, 132, 135, 139, 142, 146, 148, 150, 152, 173, 182, 190, 193, 202, 216, 221, 222
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OFFSET
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1,2
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EXAMPLE
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phi(19)=18, (6*18-1,6*18+1) = (107,109) = (A000040(28), A000040(29)), therefore 19 is a term;
phi(20)=8, (6*8-1,6*8+1) = (47,49) = (A000040(15),7*7), therefore 20 is not a term;
phi(21)=12, (6*12-1,6*12+1) = (71,73) = (A000040(20), A000040(21)), therefore 19 is a term.
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CROSSREFS
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Cf. A001359, A006512, A014574.
Sequence in context: A084166 A018297 A050886 this_sequence A116853 A066615 A133951
Adjacent sequences: A079307 A079308 A079309 this_sequence A079311 A079312 A079313
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 10 2003
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