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Search: id:A085118
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| A085118 |
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Primes together with twice the odd primes. |
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+0
1
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| 2, 3, 5, 6, 7, 10, 11, 13, 14, 17, 19, 22, 23, 26, 29, 31, 34, 37, 38, 41, 43, 46, 47, 53, 58, 59, 61, 62, 67, 71, 73, 74, 79, 82, 83, 86, 89, 94, 97, 101, 103, 106, 107, 109, 113, 118, 122, 127, 131, 134, 137, 139, 142, 146, 149, 151, 157, 158, 163, 166, 167, 173, 178
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Probably the same sequence as: numbers n such that phi(n)+1 divides n.
Comment from Francisco Salinas (franciscodesalinas(AT)hotmail.com), Apr 25 2004: Cohen and Segal showed that in case there were other solutions to this problem (which appeared to be posed by Schinzel), then they should have at least 15 distinct prime factors. Moreover, there is a connection with the Lehmer's totient problem which asks whether there is a composite n such that phi(n)|(n-1). If no such composite exist then p and 2p are the only members for Leroy's sequence.
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REFERENCES
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G. L. Cohen; S. L. Segal, A note concerning those n for which phi(n)+1 divides n. Fibonacci Quarterly 27 (1989), no. 3, pp. 285-286.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
Eric Weisstein's World of Mathematics, Lehmer's Totient Problem
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CROSSREFS
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Cf. A068422.
Sequence in context: A087006 A144147 A068422 this_sequence A166158 A137313 A117204
Adjacent sequences: A085115 A085116 A085117 this_sequence A085119 A085120 A085121
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KEYWORD
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nonn,easy
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AUTHOR
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Leroy Quet Apr 25 2004
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jan 27 2005
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