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A014202
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Number of solutions to x^2+x*y+y^2 <= n, excluding (0,0), divided by 6.
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1
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0, 1, 1, 2, 3, 3, 3, 5, 5, 6, 6, 6, 7, 9, 9, 9, 10, 10, 10, 12, 12, 14, 14, 14, 14, 15, 15, 16, 18, 18, 18, 20, 20, 20, 20, 20, 21, 23, 23, 25, 25, 25, 25, 27, 27, 27, 27, 27, 28, 31, 31, 31, 33, 33, 33, 33, 33, 35, 35, 35
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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FORMULA
| for n>0 a(n)=sum(k=1,n,K(k,3)*floor(n/k)) where K(x,y) is the Kronecker symbol. [From Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 31 2009]
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PROG
| (PARI) a(n)=if(n<1, 0, sum(k=1, n, kronecker(k, 3)*floor(n/k))) [From Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 31 2009]
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CROSSREFS
| A014201/6. Cf. A014200.
Sequence in context: A087418 A087731 A141784 * A145281 A151687 A160573
Adjacent sequences: A014199 A014200 A014201 * A014203 A014204 A014205
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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