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Search: id:A027692
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| A027692 |
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Numbers of form n^2 + (n+7). |
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+0
3
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| 7, 9, 13, 19, 27, 37, 49, 63, 79, 97, 117, 139, 163, 189, 217, 247, 279, 313, 349, 387, 427, 469, 513, 559, 607, 657, 709, 763, 819, 877, 937, 999, 1063, 1129, 1197, 1267, 1339, 1413, 1489, 1567, 1647, 1729, 1813, 1899, 1987, 2077, 2169, 2263
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Integers k for which the discriminant of x^3-kx-k is a square. [From Jacob A. Siehler (siehlerj(AT)wlu.edu), Mar 14 2009]
Except for the first term, a(n)=2*n+a(n-1), (with a(1)=9) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Oct 23 2009]
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LINKS
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P. De Geest, Palindromic Quasi_Over_Squares of the form n^2+(n+X)
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FORMULA
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a(n)=2*n+a(n-1)-2 (with a(1)=7) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 07 2009]
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EXAMPLE
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For n=2, a(2)=2*2+7-2=9; n=3, a(3)=2*3+9-2=13; n=4, a(4)=2*4+13-2=19 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 07 2009]
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MAPLE
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with (combinat):seq(fibonacci(3, n)+n+6, n=0..47); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 07 2008
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CROSSREFS
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Cf. A002522.
Sequence in context: A051913 A129069 A125866 this_sequence A032487 A160777 A063189
Adjacent sequences: A027689 A027690 A027691 this_sequence A027693 A027694 A027695
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KEYWORD
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nonn,new
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com)
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