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Search: id:A067144
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| A067144 |
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Numbers n such that sigma(phi(n))==0 (mod n). |
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+0
1
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| 1, 3, 15, 28, 255, 744, 1209, 2418, 20440, 65535, 548856, 2835756, 4059264, 4451832, 10890040, 13192608, 23001132, 23746333, 27474741, 54949482, 55385589, 110771178, 220174080, 222850677, 445701354
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OFFSET
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1,2
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COMMENT
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Sequence A018784 consists of solutions to sigma(phi(n))=n. If n is in A018784, or if n is odd and 2n is in A018784 (e.g. n=1209), then n is in this sequence.
Are there any other terms? Answer from Vim Wenders (vim(AT)gmx.li), Nov 11 2006: Yes. 23746333 is present. sigma(phi(23746333))/23746333 = 3, and neither 23746333 nor 47492666 are in A018784.
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CROSSREFS
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Cf. A018784.
Adjacent sequences: A067141 A067142 A067143 this_sequence A067145 A067146 A067147
Sequence in context: A050848 A077785 A015646 this_sequence A018784 A053519 A039666
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KEYWORD
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more,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 18 2002
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EXTENSIONS
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Edited by Dean Hickerson (dean(AT)math.ucdavis.edu), Feb 20 2002
More terms from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Nov 28 2004
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