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Search: id:A157913
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| 48, 240, 560, 1008, 1584, 2288, 3120, 4080, 5168, 6384, 7728, 9200, 10800, 12528, 14384, 16368, 18480, 20720, 23088, 25584, 28208, 30960, 33840, 36848, 39984, 43248, 46640, 50160, 53808, 57584, 61488, 65520, 69680, 73968, 78384, 82928
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OFFSET
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1,1
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COMMENT
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If A=[A157913] 64*n.^2-16 (48, 240, 560,.,); Y=[A000027] n (1, 2, 3, 4, ,.,); X=[A157914] 8*n^2 - 1 (n>0, 7, 31, 71..,), we have, for all terms, Pell's equation X^2-A*Y^2=1. Example: 7^2-48 *1\^2=1; 31^2-240*2^2=1; 71^2-560*3^2=1.
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LINKS
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Edward Everett Withford, Pell Equation
Wolfram MathWorld, Pell Equation
Vincenzo Librandi, X^2-AY^2=1
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FORMULA
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a(n)=64*n^2-16 (n>0)
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EXAMPLE
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For n=1, a(1)=48; n=2, a(2)=240; n=3, a(3)=560
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CROSSREFS
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Cf. A000027, A157914
Sequence in context: A072254 A062248 A100146 this_sequence A052683 A115056 A001337
Adjacent sequences: A157910 A157911 A157912 this_sequence A157914 A157915 A157916
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KEYWORD
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nonn
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AUTHOR
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Vincenzo Librandi (vincenzo.librandi(AT)in.it), Mar 09 2009
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