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, 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

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: A092348 A274772 A369177 * A338512 A006528 A052749

Adjacent sequences: A234268 A234269 A234270 * A234272 A234273 A234274

Keyword

nonn

Author

N. J. A. Sloane, Dec 24 2013

Status

approved