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Search: id:A058306
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| A058306 |
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Denominator of H(n), where H(0)=-1/12, H(n) = number of equivalence classes of positive definite quadratic forms a*x^2+b*x*y+c*y^2 with discriminant b^2-4ac = -n, counting forms equivalent to x^2+y^2 (resp. x^2+x*y+y^2) with multiplicity 1/2 (resp. 1/3). |
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+0
2
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| 12, 1, 1, 3, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(n) = 0 if n = 1 or 2 (mod 4).
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REFERENCES
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D. Zagier, The Eichler-Selberg Trace Formula on SL_2(Z), Appendix to S. Lang, Introduction to Modular Forms, Springer, 1976.
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EXAMPLE
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-1/12, 0, 0, 1/3, 1/2, 0, 0, 1, 1, ...
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CROSSREFS
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Cf. A058305.
Sequence in context: A012454 A010208 A010209 this_sequence A010207 A010206 A070636
Adjacent sequences: A058303 A058304 A058305 this_sequence A058307 A058308 A058309
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KEYWORD
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nonn,frac
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Dec 09 2000
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