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A234271 G.f.: (1+4*x+10*x^2+4*x^3+x^4)/(1-2*x-2*x^2-2*x^3+x^4). 1
1, 6, 24, 66, 192, 558, 1608, 4650, 13440, 38838, 112248, 324402, 937536, 2709534, 7830696, 22631130, 65405184, 189024486, 546290904, 1578810018, 4562845632, 13186868622, 38110757640, 110142133770, 318316674432, 919952263062, 2658711384888, 7683818510994, 22206647643456, 64178402815614 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

J. Choi, N. Pippenger, Counting the Angels and Devils in Escher's Circle Limit IV, arXiv preprint arXiv:1310.1357 [math.CO], 2013.

Index entries for linear recurrences with constant coefficients, signature (2,2, 2,-1).

MATHEMATICA

CoefficientList[Series[(1+4x+10x^2+4x^3+x^4)/(1-2x-2x^2-2x^3+x^4), {x, 0, 30}], x] (* Harvey P. Dale, Apr 12 2017 *)

Join[{1}, LinearRecurrence[{2, 2, 2, -1}, {6, 24, 66, 192}, 50]] (* Vincenzo Librandi, Apr 14 2017 *)

PROG

(MAGMA) I:=[1, 6, 24, 66, 192]; [n le 5 select I[n] else 2*Self(n-1)+2*Self(n-2)+2*Self(n-3)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Apr 14 2017

(PARI) x='x + O('x^30); Vec((1 + 4*x + 10*x^2 + 4*x^3 + x^4)/(1 - 2*x - 2*x^2 - 2*x^3 + x^4)) \\ Indranil Ghosh, Apr 14 2017

CROSSREFS

Sequence in context: A270851 A092348 A274772 * A006528 A052749 A262445

Adjacent sequences:  A234268 A234269 A234270 * A234272 A234273 A234274

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 24 2013

STATUS

approved

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Last modified October 17 07:57 EDT 2018. Contains 316276 sequences. (Running on oeis4.)