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A152035 G.f.: (1-2*x^2)/(1-2*x-2*x^2). 2
1, 2, 4, 12, 32, 88, 240, 656, 1792, 4896, 13376, 36544, 99840, 272768, 745216, 2035968, 5562368, 15196672, 41518080, 113429504, 309895168, 846649344, 2313089024, 6319476736, 17265131520, 47169216512, 128868696064, 352075825152, 961889042432, 2627929735168, 7179637555200, 19615134580736 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Essentially same as A028860. - Philippe Deléham, Sep 21 2009

LINKS

Table of n, a(n) for n=0..31.

FORMULA

a(n) = 2*(a(n-1) + a(n-2)) for n >= 3. - Peter Luschny, Jan 03 2019

MAPLE

a := proc(n) option remember;

`if`(n < 3, [1, 2, 4][n+1], 2*(a(n-1) + a(n-2))) end:

seq(a(n), n=0..31); # Peter Luschny, Jan 03 2019

MATHEMATICA

f[n_] = 2^n*Product[(1 + 2*Cos[k*Pi/n]^2), {k, 1, Floor[(n - 1)/2]}]; Table[FullSimplify[ExpandAll[f[n]]], {n, 0, 15}]

CoefficientList[Series[(1-2x^2)/(1-2x-2x^2), {x, 0, 40}], x] (* Harvey P. Dale, Sep 23 2014 *)

CROSSREFS

Cf. A028860. Row sums of A322942.

Sequence in context: A181329 A293007 A028860 * A026151 A025178 A231295

Adjacent sequences:  A152032 A152033 A152034 * A152036 A152037 A152038

KEYWORD

nonn,easy

AUTHOR

Roger L. Bagula, Nov 20 2008

EXTENSIONS

Edited by N. J. A. Sloane, Apr 11 2009, based on comments from Philippe Deléham and R. J. Mathar

More terms from Philippe Deléham, Sep 21 2009

STATUS

approved

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Last modified August 8 11:31 EDT 2020. Contains 336298 sequences. (Running on oeis4.)