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A291462 a(n) = (1/2)*A291417(n).. 2
2, 9, 38, 161, 680, 2872, 12128, 51214, 216264, 913228, 3856328, 16284284, 68764352, 290374208, 1226175744, 5177825416, 21864627616, 92328709904, 389880441696, 1646365025296, 6952176889728, 29357258422912, 123968166486528, 523485745182432, 2210545926231680 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Clark Kimberling, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (4, 2, -4, -2)

FORMULA

G.f.: -(((-1 + x) (1 + x) (2 + x))/(1 - 4 x - 2 x^2 + 4 x^3 + 2 x^4)).

a(n) = 4*a(n-1) + 2*a(n-2) - 4*a(n-3) - 2*a(n-4) for n >= 5.

MATHEMATICA

z = 60; s = x + x^2; p = 1 - 4 s + 2 s^2;

Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]  (* A019590 *)

u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A291417 *)

u / 2  (*A291462)

CROSSREFS

Cf. A019590, A291382, A291417.

Sequence in context: A291265 A037489 A037569 * A001077 A150993 A150994

Adjacent sequences:  A291459 A291460 A291461 * A291463 A291464 A291465

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Sep 07 2017

STATUS

approved

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Last modified February 22 18:00 EST 2018. Contains 299469 sequences. (Running on oeis4.)