A128074 a(n) = (n^3+n)*9^n.

0, 18, 810, 21870, 446148, 7676370, 117979902, 1674039150, 22384294920, 285916320882, 3521652245010, 42113381995278, 491427393476940, 5617523480607090, 63094193590782438, 697970937800860110

Offset: 0

Author

Mohammad K. Azarian, May 02 2007

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000 (corrected by Ray Chandler, Jan 19 2019)
• Index entries for linear recurrences with constant coefficients, signature (36,-486,2916,-6561).

Crossrefs

Cf. A128796; A128960; A128985; A129002.

Programs

Magma

[(n^3 + n) * 9^n: n in [1..20]]; // Vincenzo Librandi, Feb 22 2012

Mathematica

Table[(n^3+n)9^n,{n,20}] (* or *) LinearRecurrence[{36,-486,2916,-6561}, {18,810,21870,446148},20] (* Harvey P. Dale, Jun 16 2011 *)

PARI

A128074(n)=(n^3+n)*9^n \\ M. F. Hasler, Oct 06 2014

Formula

a(1)=18, a(2)=810, a(3)=21870, a(4)=446148, a(n)=36*a(n-1)- 486*a(n-2)+ 2916*a(n-3)-6561*a(n-4). - Harvey P. Dale, Jun 16 2011

G.f.: 18*x*(1+9*x+81*x^2)/(1-9*x)^4. - Harvey P. Dale, Jun 16 2011

Extensions

Extended to a(0)=0 by M. F. Hasler, Oct 06 2014