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A039957
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Squarefree numbers congruent to 3 mod 4.
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9
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3, 7, 11, 15, 19, 23, 31, 35, 39, 43, 47, 51, 55, 59, 67, 71, 79, 83, 87, 91, 95, 103, 107, 111, 115, 119, 123, 127, 131, 139, 143, 151, 155, 159, 163, 167, 179, 183, 187, 191, 195, 199, 203, 211, 215, 219, 223, 227, 231, 235, 239, 247, 251, 255
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Negative of odd fundamental discriminants D := b^2-4*a*c<0 of definite integer binary quadratic forms F=a*x^2+b*x*y+c*y^2. See Buell reference pp. 224-230. See 4*A089269 for the even case and A003657 for combined even and odd numbers. - Wolfdieter Lang, Nov 07 2003
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REFERENCES
| R. A. Mollin, Quadratics, CRC Press, 1996, Tables B1-B3.
D. A. Buell, Binary Quadratic Forms. Springer-Verlag, NY, 1989.
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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MATHEMATICA
| fQ[n_] := SquareFreeQ[n] && Mod[n, 4] == 3; Select[ Range@ 258, fQ] (* RGWv, Mar 02 2011 *)
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PROG
| (MAGMA) [4*n+3: n in [0..63] | IsSquarefree(4*n+3)]; // Bruno Berselli, Mar 04 2011
(Haskell)
a039957 n = a039957_list !! (n-1)
a039957_list = filter ((== 3) . (`mod` 4)) a005117_list
-- Reinhard Zumkeller, Aug 15 2011
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CROSSREFS
| Cf. A039955, A039956.
Sequence in context: A131098 A118894 A194397 * A079422 A194442 A034934
Adjacent sequences: A039954 A039955 A039956 * A039958 A039959 A039960
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KEYWORD
| nonn,easy,nice
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AUTHOR
| R. K. Guy (rkg(AT)cpsc.ucalgary.ca)
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EXTENSIONS
| Offset corrected
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