A121203 a(n) = 2n+7^n-5^n.

0, 4, 28, 224, 1784, 13692, 102036, 745432, 5374192, 38400500, 272709644, 1928498640, 13597146600, 95668307308, 672119557252, 4717043931848, 33080342679008, 231867574534116, 1624598900644860, 11379821699045056

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (14,-60,82,-35).

Formula

G.f.: 4*x*(1-7*x+18*x^2)/((1-x)^2*(1-5*x)*(1-7*x)). - Vincenzo Librandi, Feb 25 2013

a(n) = 14*a(n-1)-60*a(n-2)+82*a(n-3)-35*a(n-4). - Vincenzo Librandi, Feb 26 2013

Mathematica

CoefficientList[Series[4 x (1 - 7 x + 18 x^2)/((1-x)^2 (1-5 x)(1-7 x)), {x, 0, 30}], x] (* Vincenzo Librandi, Feb 25 2013 *)

Prog

(Magma) [2*n+7^n-5^n: n in [0..30]]; // Vincenzo Librandi, Feb 26 2013
(Magma) I:=[0, 4, 28, 224]; [n le 4 select I[n] else 14*Self(n-1)-60*Self(n-2)+82*Self(n-3)-35*Self(n-4): n in [1..20]]; // Vincenzo Librandi, Feb 26 2013

Crossrefs

Cf. A074616.

Sequence in context: A026033 A005810 A371755 * A368234 A192620 A180708

Adjacent sequences: A121200 A121201 A121202 * A121204 A121205 A121206

Keyword

nonn,easy

Author

Mohammad K. Azarian, Aug 19 2006

Extensions

Edited by Ray Chandler, Sep 06 2006

Status

approved