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A135790
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Positive numbers of the form -x^4+6x^2 y^2-y^4 (where x,y are integers).
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7
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4, 7, 64, 112, 119, 164, 239, 324, 527, 567, 644, 959, 1024, 1519, 1792, 1904, 2047, 2500, 2624, 2884, 3479, 3824, 4207, 4324, 4375, 4879, 4964, 5184, 5572, 6647, 6887, 7327, 8119, 8432, 9072, 9604, 9639
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OFFSET
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1,1
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COMMENTS
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Squares of these numbers are of the form N^4-M^2 (where N belongs to A135786 and M to A057102) Proof uses: (x^4 - 6x^2 y^2 + y^4)^2=(x^2+y^2)^4-(4(x^3y-xy^2))^2
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LINKS
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Table of n, a(n) for n=1..37.
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MATHEMATICA
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a = {}; Do[Do[w = -x^4 + 6x^2 y^2 - y^4; If[w > 0&&w<10000, AppendTo[a, w]], {x, y, 2000}], {y, 1, 2000}]; Union[a]
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CROSSREFS
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Cf. A000404, A050803, A057102, A135784, A060803, A135786, A135787, A135789.
Sequence in context: A060413 A065674 A072954 * A156474 A136276 A220003
Adjacent sequences: A135787 A135788 A135789 * A135791 A135792 A135793
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski, Nov 29 2007
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STATUS
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approved
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