A291386 a(n) = (1/3)*A099432(n+1).

2, 11, 54, 252, 1134, 4977, 21438, 91017, 381996, 1588248, 6552252, 26853687, 109438938, 443837799, 1792373346, 7211142612, 28915704810, 115603540605, 460942202070, 1833459620517, 7276826042712, 28823185892016, 113957884236024, 449793742386627

Offset

0,1

Links

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

Index entries for linear recurrences with constant coefficients, signature (6, -3, -18, -9)

Formula

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

a(n) = 6*a(n-1) - 3*a(n-2) - 18*a(n-3) - 9*a(n-4) for n >= 5.

Mathematica

z = 60; s = x + x^2; p = (1 - 3 s)^2;
Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]  (* A019590 *)
u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A099432 *)
u / 3  (* A291386 *)
LinearRecurrence[{6, -3, -18, -9}, {2, 11, 54, 252}, 30] (* Harvey P. Dale, Oct 06 2017 *)

Crossrefs

Cf. A019590, A291382, A099432.

Sequence in context: A063767 A307568 A161559 * A128748 A251662 A327215

Adjacent sequences: A291383 A291384 A291385 * A291387 A291388 A291389

Keyword

nonn,easy

Author

Clark Kimberling, Sep 04 2017

Status

approved