A128803 - OEIS

%I #17 Sep 08 2022 08:45:30

%S 0,0,162,4374,78732,1180980,15943230,200884698,2410616376,27894275208,

%T 313810596090,3451916556990,37280698815492,396531069219324,

%U 4163576226802902,43237137739876290,444724845324441840

%N n*(n-1)*9^n.

%H Vincenzo Librandi, <a href="/A128803/b128803.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (27,-243,729).

%F G.f.: 162*x^2/(1-9*x)^3. - _Vincenzo Librandi_, Feb 12 2013

%F a(n) = 27*a(n-1)-243*a(n-2)+729*a(n-3). - _Vincenzo Librandi_, Feb 12 2013

%F a(n) = 162*A081139(n). - _R. J. Mathar_, Apr 26 2015

%t 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 *)

%o (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

%Y Cf. A036289, A007758.

%K nonn,easy

%O 0,3

%A _Mohammad K. Azarian_, Apr 07 2007