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A079896
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Discriminants of indefinite binary quadratic forms.
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8
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5, 8, 12, 13, 17, 20, 21, 24, 28, 29, 32, 33, 37, 40, 41, 44, 45, 48, 52, 53, 56, 57, 60, 61, 65, 68, 69, 72, 73, 76, 77, 80, 84, 85, 88, 89, 92, 93, 96, 97, 101, 104, 105, 108, 109, 112, 113, 116, 117, 120, 124, 125, 128, 129, 132, 133, 136, 137, 140, 141, 145, 148
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| For an indefinite binary quadratic form over the integers a*x^2 + b*x*y + c*y^2 the discriminant is D = b^2 - 4*a*c > 0; and D not a square is assumed.
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REFERENCES
| A. Scholz and B. Schoeneberg, Einfuehrung in die Zahlentheorie, 5. Aufl., de Gruyter, Berlin, New York, 1973, p. 112.
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LINKS
| S. R. Finch, Class number theory
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FORMULA
| a(n) is 0 (mod 4) or 1 (mod 4), but not a square.
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MATHEMATICA
| Select[ Range[148], (Mod[ #, 4] == 0 || Mod[ #, 4] == 1) && !IntegerQ[ Sqrt[ # ]] & ]
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CROSSREFS
| Cf. A014601, A042948 (with squares).
Sequence in context: A133269 A076635 A116602 * A133315 A003658 A003656
Adjacent sequences: A079893 A079894 A079895 * A079897 A079898 A079899
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KEYWORD
| nonn,easy
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AUTHOR
| Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Jan 31 2003
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 26 2003
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