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Search: id:A070999
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| A070999 |
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Numbers n such that the denominator of sum(k=1,n,1/gcd(n,k)) is not equal to n. |
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+0
1
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| 6, 15, 18, 21, 30, 33, 35, 42, 44, 45, 48, 51, 54, 60, 66, 69, 70, 78, 84, 87, 90, 99, 102, 105, 114, 119, 120, 123, 126, 132, 133, 135, 138, 140, 141, 144, 147, 150, 153, 159, 162, 165, 168, 174, 177, 180, 186, 195, 198, 204, 207, 210, 213, 217, 220, 221, 222
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Does lim n -> infinity a(n)/n = 3 ?
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EXAMPLE
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sum(k=1,6,1/gcd(6,k))=7/2 hence 6 is in the sequence but sum(k=1,12,1/gcd(12,k))=77/12 so 12 is not in the sequence.
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PROGRAM
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(PARI) for(n=1, 300, if(denominator(sum(i=1, n, 1/gcd(n, i)))<n, print1(n, ", ")))
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CROSSREFS
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Sequence in context: A122661 A133481 A099535 this_sequence A128693 A105285 A138922
Adjacent sequences: A070996 A070997 A070998 this_sequence A071000 A071001 A071002
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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), May 18 2002
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