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Search: id:A068991
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| A068991 |
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Numbers n such that sum( d divides n, sigma(d)/phi(d)) is an integer. |
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+0
2
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| 1, 2, 3, 6, 10, 21, 30, 42, 78, 110, 210, 330, 390, 930, 1218, 1830, 2025, 2310, 2530, 4050, 4134, 4290, 6090, 7590, 14175, 14910, 22110, 28350, 51090, 52650, 53130, 66990, 71862, 98670, 118910, 159975
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OFFSET
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1,2
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COMMENT
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Conjecture : if n is in the sequence and n is squarefree then the denominator of the 2n-th Bernoulli's number contains n. E.g. 2310 is squarefree, is in the sequence and A002445(2310)=744535159372016163713900138929458330 is divisible by 2310.
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CROSSREFS
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Sequence in context: A120707 A047111 A106741 this_sequence A008928 A124343 A032291
Adjacent sequences: A068988 A068989 A068990 this_sequence A068992 A068993 A068994
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KEYWORD
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easy,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 06 2002
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