A128800 a(n) = n*(n-1)*6^n.

0, 0, 72, 1296, 15552, 155520, 1399680, 11757312, 94058496, 725594112, 5441955840, 39907676160, 287335268352, 2037468266496, 14262277865472, 98738846760960, 677066377789440, 4604051368968192, 31077346740535296

Offset

0,3

Links

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

Index entries for linear recurrences with constant coefficients, signature (18,-108,216).

Formula

G.f.: 72*x^2/(1 - 6*x)^3. - Vincenzo Librandi, Feb 11 2013

a(n) = 72*A081136(n). - R. J. Mathar, Apr 26 2015

a(n) = 18*a(n-1) - 108*a(n-2) + 216*a(n-3). - Wesley Ivan Hurt, Jan 20 2024

Mathematica

CoefficientList[Series[72 x^2/(1 - 6 x)^3, {x, 0, 30}], x] (* Vincenzo Librandi, Feb 11 2013 *)
LinearRecurrence[{18, -108, 216}, {0, 0, 72}, 30] (* Harvey P. Dale, Mar 22 2018 *)

Prog

(Magma) [(n^2-n)*6^n: n in [0..25]]; // Vincenzo Librandi, Feb 11 2013

Crossrefs

Cf. A036289, A007758.

Sequence in context: A269074 A200556 A239423 * A367781 A008391 A292881

Adjacent sequences: A128797 A128798 A128799 * A128801 A128802 A128803

Keyword

nonn,easy

Author

Mohammad K. Azarian, Apr 07 2007

Status

approved