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
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Apr 07 2007
STATUS
approved