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Search: id:A090735
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| A090735 |
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Number of positive square-free numbers <=n that can be expressed as a sum of 2 squares >0. |
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+0
1
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| 0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16, 17, 17
(list; graph; listen)
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OFFSET
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1,5
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REFERENCES
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S. R. Finch, Mathematical Constants, Cambridge, 2003, p. 100
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FORMULA
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a(n) is asymptotic to (6K/Pi^2)*n/sqrt(log(x)) where K is the Landau-Ramanujan constant
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PROGRAM
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(PARI) a(n)=sum(i=1, n, issquarefree(i)*if(sum(u=1, i, sum(v=1, u, if(u^2+v^2-i, 0, 1))), 1, 0))
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CROSSREFS
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Cf. A064533.
Sequence in context: A025809 A114575 A131849 this_sequence A090736 A094999 A120202
Adjacent sequences: A090732 A090733 A090734 this_sequence A090736 A090737 A090738
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Jan 18 2004
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