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A133288
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Negative discriminants with form class group of exponent 2 (negated).
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5
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15, 20, 24, 32, 35, 36, 40, 48, 51, 52, 60, 64, 72, 75, 84, 88, 91, 96, 99, 100, 112, 115, 120, 123, 132, 147, 148, 160, 168, 180, 187, 192, 195, 228, 232, 235, 240, 267, 280, 288, 312, 315, 340, 352, 372, 403, 408, 420, 427, 435, 448, 480, 483, 520, 532, 555, 595, 627, 660, 672, 708, 715, 760
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OFFSET
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1,1
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REFERENCES
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D. A. Cox, Primes of the form x^2+ny^2, Wiley, New York, 1989.
D. E. Flath, Introduction to Number Theory, Wiley-Interscience, 1989.
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LINKS
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PROG
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(PARI) ok(n)={(-n)%4<2 && quadclassunit(-n).no > 1 && !#select(k->k<>2, quadclassunit(-n).cyc)} \\ Andrew Howroyd, Jul 20 2018
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CROSSREFS
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KEYWORD
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fini,nonn
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AUTHOR
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STATUS
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approved
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