A128803 n*(n-1)*9^n.

0, 0, 162, 4374, 78732, 1180980, 15943230, 200884698, 2410616376, 27894275208, 313810596090, 3451916556990, 37280698815492, 396531069219324, 4163576226802902, 43237137739876290, 444724845324441840

Offset

0,3

Links

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

Index entries for linear recurrences with constant coefficients, signature (27,-243,729).

Formula

G.f.: 162*x^2/(1-9*x)^3. - Vincenzo Librandi, Feb 12 2013

a(n) = 27*a(n-1)-243*a(n-2)+729*a(n-3). - Vincenzo Librandi, Feb 12 2013

a(n) = 162*A081139(n). - R. J. Mathar, Apr 26 2015

Mathematica

LinearRecurrence[{27, -243, 729}, {0, 0, 162}, 30] (* or *) CoefficientList[Series[162 x^2/(1 - 9 x)^3, {x, 0, 30}], x] (* Vincenzo Librandi, Feb 12 2013 *)

Prog

(Magma) [(n^2-n)*9^n: n in [0..25]]; /* or */ I:=[0, 0, 162]; [n le 3 select I[n] else 27*Self(n-1)-243*Self(n-2)+729*Self(n-3): n in [1..25]]; // Vincenzo Librandi, Feb 12 2013

Crossrefs

Cf. A036289, A007758.

Sequence in context: A249295 A221871 A245955 * A035746 A285046 A022151

Adjacent sequences: A128800 A128801 A128802 * A128804 A128805 A128806

Keyword

nonn,easy

Author

Mohammad K. Azarian, Apr 07 2007

Status

approved