A128788 a(n) = n^2*9^n.

0, 9, 324, 6561, 104976, 1476225, 19131876, 234365481, 2754990144, 31381059609, 348678440100, 3797108212689, 40669853253264, 429575324987601, 4483851321172356, 46325504721296025, 474373168346071296

Offset: 0

Author

Mohammad K. Azarian, Apr 07 2007

Keywords

• nonn
• easy

Comments

Subsequence of A008854 and A047462. [Bruno Berselli, Feb 07 2013]

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (27,-243,729).

Crossrefs

Cf. A007758, A008854, A036289, A047462.

Programs

Magma

[n^2*9^n: n in [0..20]]; // Vincenzo Librandi, Feb 07 2013

Mathematica

CoefficientList[Series[9 x (1 + 9 x)/(1 - 9 x)^3, {x, 0, 30}], x] (* or *) LinearRecurrence[{27, -243, 729}, {0, 9, 324}, 20] (* Vincenzo Librandi, Feb 07 2013 *)

Formula

G.f.: 9*x*(1+9*x)/(1-9*x)^3. - Vincenzo Librandi, Feb 07 2013

a(n) = 27*a(n-1) - 243*a(n-2) + 729*a(n-3). - Vincenzo Librandi, Feb 07 2013