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A066373 a(n) = (3*n-2)*2^(n-3). 7
2, 7, 20, 52, 128, 304, 704, 1600, 3584, 7936, 17408, 37888, 81920, 176128, 376832, 802816, 1703936, 3604480, 7602176, 15990784, 33554432, 70254592, 146800640, 306184192, 637534208, 1325400064, 2751463424, 5704253440 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

An elephant sequence, see A175654. For the corner squares 16 A[5] vectors, with decimal values between 59 and 440, lead to this sequence (with a leading 1 added). For the central square these vectors lead to the companion sequence A098156 (without a(1)). - Johannes W. Meijer, Aug 15 2010

LINKS

Harry J. Smith, Table of n, a(n) for n = 2..200

M. Azaola and F. Santos, The number of triangulations of the cyclic polytope C(n,n-4), Discrete Comput. Geom., 27 (2002), 29-48.

Index entries for linear recurrences with constant coefficients, signature (4,-4).

FORMULA

G.f.: x^2*(2-x)/(1-2x)^2. - Emeric Deutsch, Jul 23 2006

a(n) = 2*a(n-1) +3*2^(n-3). - Vincenzo Librandi, Mar 20 2011

a(n+1) - a(n) = A098156(n). - R. J. Mathar, Apr 25 2013

From Paul Curtz, Jun 29 2018: (Start)

a(n) = A130129(n-2) - A130129(n-3) for n >= 2.

Binomial transform of A016789.

Inverse binomial transform of A288834.

Also the main diagonal of the difference table of m -> (-1)^m*(m+2).

    2,  -3,   4,  -5, ...

   -5,   7,  -9,  11, ...

   12, -16,  20, -24, ...

  -28,  36, -44,  52, ... . (End)

MAPLE

seq((3*n-2)*2^(n-3), n=2..30); # Emeric Deutsch, Jul 23 2006

MATHEMATICA

Array[(3 # - 2)*2^(# - 3) &, 28, 2] (* or *)

Drop[CoefficientList[Series[x^2*(2 - x)/(1 - 2 x)^2, {x, 0, 29}], x], 2] (* Michael De Vlieger, Jun 30 2018 *)

PROG

(PARI) { for (n=2, 200, write("b066373.txt", n, " ", (3*n - 2)*2^(n - 3)) ) } /* Harry J. Smith, Feb 11 2010 */

CROSSREFS

Column k=2 of A229079.

Cf. A016789, A098156, A130129, A288834.

Sequence in context: A335927 A261054 A134311 * A096005 A050532 A050513

Adjacent sequences:  A066370 A066371 A066372 * A066374 A066375 A066376

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Jan 04 2002

STATUS

approved

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Last modified August 4 16:34 EDT 2020. Contains 336202 sequences. (Running on oeis4.)