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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 21 02:19 EST 2018. Contains 299388 sequences. (Running on oeis4.)