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Search: id:A157918
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| 600, 2475, 5600, 9975, 15600, 22475, 30600, 39975, 50600, 62475, 75600, 89975, 105600, 122475, 140600, 159975, 180600, 202475, 225600, 249975, 275600, 302475, 330600, 359975, 390600, 422475, 455600, 489975, 525600, 562475, 600600, 639975
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If A=[A157918] 625*n.^2-25 (600, 2475, 5600,.,); Y=[A005843] 2n (2,4,6,8, ,.,); X=[A157919] 50*n^2- 1 (49, 199, 449.,), we have, for all terms, Pell's equation X^2-A*Y^2=1. Example: 49^2-600 *2\^2=1; 199^2-2475*4^2=1; 449^2-5600*6^2=1.
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LINKS
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Edward Everett Withford, Pell Equation
Vincenzo Librandi, X^2-AY^2=1
Wolfram MathWorld, Pell Equation
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FORMULA
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a(n)=625*n^2-25 (n>0)
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EXAMPLE
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For n=1, a(1)=600; n=2, a(2)=2475; n=3, a(3)=5600
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CROSSREFS
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Cf. A005843, A157919
Sequence in context: A106762 A158277 A090222 this_sequence A092183 A048530 A023915
Adjacent sequences: A157915 A157916 A157917 this_sequence A157919 A157920 A157921
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KEYWORD
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nonn
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AUTHOR
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Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 09 2009
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