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A169724
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(2*3^(n-1)+1)^2.
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1
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9, 49, 361, 3025, 26569, 237169, 2128681, 19140625, 172213129, 1549760689, 13947373801, 125524947025, 1129720271689, 10167469690609, 91507188951721, 823564585774225, 7412080927594249, 66708727315226929, 600378542737678441, 5403406875341014225
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OFFSET
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1,1
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COMMENTS
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A subsequence of the squares A000290.
Essentially equal to A052919(n)^2.
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Alice V. Kleeva, Grid for this sequence
Alice V. Kleeva, Illustration of initial terms
Index to sequences with linear recurrences with constant coefficients, signature (13,-39,27).
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FORMULA
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a(n)= +13*a(n-1) -39*a(n-2) +27*a(n-3). G.f.: x*( -9+68*x-75*x^2 ) / ( (x-1)*(3*x-1)*(9*x-1) ). [R. J. Mathar, Apr 26 2010]
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MATHEMATICA
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CoefficientList[Series[(-9 + 68 x - 75 x^2)/((x - 1) (3 x - 1) (9 x - 1)), {x, 0, 40}], x] (* Vincenzo Librandi, Dec 03 2012 *)
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PROG
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(MAGMA) I:=[9, 49, 361]; [n le 3 select I[n] else 13*Self(n-1) - 39*Self(n-2) + 27*Self(n-3): n in [1..30]]; // Vincenzo Librandi, Dec 03 2012
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CROSSREFS
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Cf. A169720-A169727, A100702.
Sequence in context: A188235 A066558 A168597 * A135625 A160603 A115326
Adjacent sequences: A169721 A169722 A169723 * A169725 A169726 A169727
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KEYWORD
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nonn,easy
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AUTHOR
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Alice V. Kleeva (alice27353(AT)gmail.com), Jan 19 2010
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EXTENSIONS
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G.f. adapted to the offset by Vincenzo Librandi, Dec 03 2012
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STATUS
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approved
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