A121517 a(n) = 4*a(n-1) + 4*a(n-2) - a(n-3); a(0)=1, a(1)=1, a(2)=7.

1, 1, 7, 31, 151, 721, 3457, 16561, 79351, 380191, 1821607, 8727841, 41817601, 200360161, 959983207, 4599555871, 22037796151, 105589424881, 505909328257, 2423957216401, 11613876753751, 55645426552351, 266613256008007

Offset

0,3

Links

Table of n, a(n) for n=0..22.

Index entries for linear recurrences with constant coefficients, signature (4,4,-1).

Formula

a(n) = 5*a(n-1)-a(n-2)+3*(-1)^n.

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

Mathematica

LinearRecurrence[{4, 4, -1}, {1, 1, 7}, 30] (* Harvey P. Dale, Jan 28 2020 *)
CoefficientList[Series[(1-3*x-x^2)/(1-4*x-4*x^2+x^3), {x, 0, 30}], x] (* Harvey P. Dale, Jun 20 2021 *)

Crossrefs

Sequence in context: A005825 A086901 A003526 * A199216 A057620 A055625

Adjacent sequences: A121514 A121515 A121516 * A121518 A121519 A121520

Keyword

nonn,easy

Author

Philippe Deléham, Sep 08 2006

Status

approved