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 A169724 (2*3^(n-1)+1)^2. 1
 9, 49, 361, 3025, 26569, 237169, 2128681, 19140625, 172213129, 1549760689, 13947373801, 125524947025, 1129720271689, 10167469690609, 91507188951721, 823564585774225, 7412080927594249, 66708727315226929, 600378542737678441, 5403406875341014225 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A subsequence of the squares A000290. Essentially equal to A052919(n)^2. LINKS 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 Robert Munafo, Sequence A169720, and two others by Alice V. Kleeva Robert Munafo, Sequence A169720, and two others by Alice V. Kleeva [Cached copy, in pdf format, included with permission] Index entries for linear recurrences with constant coefficients, signature (13,-39,27). FORMULA 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] MATHEMATICA 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 *) PROG (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 CROSSREFS Cf. A169720-A169727, A100702. Sequence in context: A286810 A066558 A168597 * A135625 A160603 A115326 Adjacent sequences:  A169721 A169722 A169723 * A169725 A169726 A169727 KEYWORD nonn,easy AUTHOR Alice V. Kleeva (alice27353(AT)gmail.com), Jan 19 2010 EXTENSIONS G.f. adapted to the offset by Vincenzo Librandi, Dec 03 2012 STATUS approved

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Last modified February 24 13:05 EST 2020. Contains 332209 sequences. (Running on oeis4.)