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A051500 a(n) = (3^n+1)^2/4. 1
1, 4, 25, 196, 1681, 14884, 133225, 1196836, 10764961, 96864964, 871725625, 7845353476, 70607649841, 635467254244, 5719200505225, 51472790198116, 463255068736321, 4169295489486724, 37523659017960025, 337712929999378756, 3039416366507624401 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (13,-39,27).

FORMULA

a(n) = A007051(n)^2. - Michel Marcus, Jun 08 2013

From Colin Barker, Feb 10 2016: (Start)

a(n) = 13*a(n-1) - 39*a(n-2) + 27*a(n-3) for n>2.

G.f.: (1-9*x+12*x^2) / ((1-x)*(1-3*x)*(1-9*x)). (End)

MATHEMATICA

(3^Range[0, 20]+1)^2/4 (* or *) LinearRecurrence[{13, -39, 27}, {1, 4, 25}, 30] (* Harvey P. Dale, Nov 05 2016 *)

PROG

(PARI) Vec((1-9*x+12*x^2)/((1-x)*(1-3*x)*(1-9*x)) + O(x^30)) \\ Colin Barker, Feb 10 2016

CROSSREFS

Sequence in context: A060908 A322442 A036449 * A206179 A151342 A001246

Adjacent sequences:  A051497 A051498 A051499 * A051501 A051502 A051503

KEYWORD

nonn,easy

AUTHOR

Colin Mallows

STATUS

approved

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Last modified August 10 04:38 EDT 2020. Contains 336368 sequences. (Running on oeis4.)