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A291384 a(n) = (1/2)*A291383(n). 2
1, 4, 14, 49, 172, 604, 2120, 7442, 26124, 91704, 321912, 1130020, 3966752, 13924640, 48880192, 171585992, 602324816, 2114363648, 7422130912, 26054187664, 91459003200, 321052008000, 1127001041280, 3956154502688, 13887439208896, 48749604609664 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

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

FORMULA

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

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

MATHEMATICA

z = 60; s = x + x^2; p = 1 - 2 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]  (* A291383 *)

u / 2  (* A291384 *)

CROSSREFS

Cf. A019590, A291382, A291383.

Sequence in context: A071729 A278692 A071733 * A010904 A277084 A071737

Adjacent sequences:  A291381 A291382 A291383 * A291385 A291386 A291387

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Sep 04 2017

STATUS

approved

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Last modified October 18 07:00 EDT 2018. Contains 316307 sequences. (Running on oeis4.)