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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; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| 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]
For n>2: a(n) = A176271(n+1,4). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 13 2010]
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LINKS
| P. De Geest, Palindromic Quasi_Over_Squares of the form n^2+(n+X)
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
| a(n)=2*n+a(n-1) (with a(0)=7) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 05 2010]
G.f. ( -7+12*x-7*x^2 ) / (x-1)^3. - R. J. Mathar, Feb 06 2011
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EXAMPLE
| a(1)=2*1+7=9; a(2)=2*2+9=13; a(3)=2*3+13=19 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 05 2010]
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MAPLE
| with (combinat):seq(fibonacci(3, n)+n+6, n=0..47); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 07 2008
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MATHEMATICA
| f[n_]:=n^2+n+7; f[Range[0, 60]] (*From Vladimir Joseph Stephan Orlovsky, Feb 06 2011*)
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CROSSREFS
| Cf. A002522.
Sequence in context: A196091 A129069 A125866 * A185720 A032487 A160777
Adjacent sequences: A027689 A027690 A027691 * A027693 A027694 A027695
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KEYWORD
| nonn
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AUTHOR
| Patrick De Geest (pdg(AT)worldofnumbers.com)
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