A002250 a(n) = 4^n - 2*3^n.

-1, -2, -2, 10, 94, 538, 2638, 12010, 52414, 222778, 930478, 3840010, 15714334, 63920218, 258869518, 1045044010, 4208873854, 16921588858, 67944635758, 272553384010, 1092538058974, 4377125804698, 17529423925198

Offset

0,2

Links

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

Index entries for linear recurrences with constant coefficients, signature (7,-12).

Formula

G.f.: -(1-5*x)/((1-3*x)*(1-4*x)). - Bruno Berselli, Jan 25 2011

a(n) = 7*a(n-1) - 12*a(n-2) for n>1. - Bruno Berselli, Jan 25 2011

Mathematica

Table[4^n - 2 3^n, {n, 0, 30}] (* or *) CoefficientList[Series[-(1 - 5 x) / ((1 - 3 x) (1 - 4 x)), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 20 2013 *)

Prog

(Magma) [4^n-2*3^n: n in [0..30]]; // Vincenzo Librandi, Jun 20 2013
(PARI) a(n)=4^n-2*3^n \\ Charles R Greathouse IV, Jun 23 2020

Crossrefs

Cf. A005061, A000244.

Sequence in context: A232974 A181334 A032034 * A304642 A005613 A005616

Adjacent sequences: A002247 A002248 A002249 * A002251 A002252 A002253

Keyword

sign,easy

Author

N. J. A. Sloane

Status

approved