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A033198
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Discriminants of real quadratic number fields.
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0
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8, 12, 5, 24, 28, 40, 44, 13, 56, 60, 17, 76, 21, 88, 92, 104, 29, 120, 124, 33, 136, 140, 37, 152, 156, 41, 168, 172, 184, 188, 204, 53, 220, 57, 232, 236, 61, 248, 65, 264, 268, 69, 280, 284, 73, 296, 77, 312, 316, 328, 332, 85, 344, 348, 89, 364, 93, 376, 380, 97
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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REFERENCES
| D. Cox, "Primes of Form x^2 + n y^2", Wiley, 1989, p. 103.
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FORMULA
| For squarefree n >= 2, a(n)=n if n=1 mod 4 else 4n.
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MAPLE
| with(numtheory): a:= proc(n) if issqrfree(n) then RETURN(piecewise(n mod 4=1, n, 4*n)) else RETURN(NULL) fi: end: seq(a(n), n=2..150); (C. Ronaldo)
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CROSSREFS
| Sequence in context: A004473 A114404 A173457 * A072900 A203836 A166173
Adjacent sequences: A033195 A033196 A033197 * A033199 A033200 A033201
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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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EXTENSIONS
| More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 03 2005
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