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Search: id:A070919
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| A070919 |
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Card{ (x,y,z) | LCM(x,y,z)=n } where LCM(x,y,z) denote the least common multiple common divisor of (x,y,z). |
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+0
5
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| 1, 7, 7, 19, 7, 49, 7, 37, 19, 49, 7, 133, 7, 49, 49, 61, 7, 133, 7, 133, 49, 49, 7, 259, 19, 49, 37, 133, 7, 343, 7, 91, 49, 49, 49, 361, 7, 49, 49, 259, 7, 343, 7, 133, 133, 49, 7, 427, 19, 133, 49, 133, 7, 259, 49, 259, 49, 49, 7, 931, 7, 49, 133, 127, 49, 343, 7, 133
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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A048691(n) gives Card{ (x,y) | LCM(x,y)=n }
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FORMULA
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a(n)=Sum(d|n, A000005(d)^3*A008683(n/d)); Sum(k>0, a(k)/k^s)=1/zeta(s)*Sum(k>0, tau(k)^3/k^s)
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PROGRAM
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(PARI) for(n=1, 100, print1(sumdiv(n, d, numdiv(d)^3*moebius(n/d)), ", "))
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CROSSREFS
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Cf. A048691.
Sequence in context: A100635 A165138 A139126 this_sequence A070847 A053416 A094248
Adjacent sequences: A070916 A070917 A070918 this_sequence A070920 A070921 A070922
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KEYWORD
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mult,easy,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), May 20 2002
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