A129009 (n^3+n^2)*9^n.

18, 972, 26244, 524880, 8857350, 133923132, 1874923848, 24794911296, 313810596090, 3835462841100, 45565298552268, 528708092292432, 6014054549826414, 67257769817585340, 741208075540736400

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (36,-486,2916,-6561).

Formula

G.f.: 18*x*(1+18*x)/(1-9*x)^4. [R. J. Mathar, Dec 19 2008]

a(n) = 36*a(n-1)-486*a(n-2)+2916*a(n-3)-6561*a(n-4). - Vincenzo Librandi, Feb 12 2013

Mathematica

LinearRecurrence[{36, -486, 2916, -6561}, {18, 972, 26244, 524880}, 30] (* Vincenzo Librandi, Feb 12 2013 *)

Prog

(Magma) [(n^3+n^2)*9^n: n in [1..25]]; /* or */ I:=[18, 972, 26244, 524880]; [n le 4 select I[n] else 36*Self(n-1)-486*Self(n-2)+2916*Self(n-3)-6561*Self(n-4): n in [1..25]]; // Vincenzo Librandi, Feb 12 2013

Crossrefs

Cf. A128796, A036289.

Sequence in context: A356687 A123786 A333089 * A042409 A363103 A073960

Adjacent sequences: A129006 A129007 A129008 * A129010 A129011 A129012

Keyword

nonn,easy

Author

Mohammad K. Azarian, May 01 2007

Status

approved