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A128969 a(n) = (n^3 - n)*9^n. 1

%I

%S 0,486,17496,393660,7085880,111602610,1607077584,21695547384,

%T 278942752080,3451916556990,41422998683880,484649084601396,

%U 5551434969070536,62453643402043530,691794203838020640

%N a(n) = (n^3 - n)*9^n.

%H Vincenzo Librandi, <a href="/A128969/b128969.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (36,-486,2916,-6561).

%F G.f.: 486x^2/(1-9x)^4. a(n)=486*A038291(n+1,3). - _R. J. Mathar_, Dec 19 2008

%F a(n) = 36*a(n-1) -486*a(n-2) +2916*a(n-3) -6561*a(n-4). - _Vincenzo Librandi_, Feb 11 2013

%t CoefficientList[Series[486 x/(1 - 9 x)^4, {x, 0, 30}], x] (* _Vincenzo Librandi_, Feb 11 2013 *)

%o (MAGMA) [(n^3-n)*9^n: n in [0..25]]; (* or *) I:=[0, 486, 17496, 393660]; [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 11 2013

%Y Cf. A128796, A036289.

%K nonn,easy

%O 1,2

%A _Mohammad K. Azarian_, Apr 28 2007

%E Offset corrected by _Mohammad K. Azarian_, Nov 20 2008

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Last modified January 29 01:54 EST 2020. Contains 331328 sequences. (Running on oeis4.)