This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A128992 #21 Sep 08 2022 08:45:30
%S A128992 0,324,13122,314928,5904900,95659380,1406192886,19284931008,
%T A128992 251048476872,3138105960900,37971082126890,447368385785904,
%U A128992 5154903899851212,58290067175240628,648557066098144350
%N A128992 a(n) = (n^3 - n^2)*9^n.
%H A128992 Vincenzo Librandi, <a href="/A128992/b128992.txt">Table of n, a(n) for n = 1..1000</a>
%H A128992 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (36,-486,2916,-6561).
%F A128992 G.f.: 162*x^2*(2+9*x)/(1-9*x)^4. - _Vincenzo Librandi_, Feb 12 2013
%F A128992 a(n) = 36*a(n-1)-486*a(n-2)+2916*a(n-3)-6561*a(n-4). - _Vincenzo Librandi_, Feb 12 2013
%t A128992 CoefficientList[Series[162 x (2 + 9 x)/(1 - 9 x)^4, {x, 0, 30}], x] (* _Vincenzo Librandi_, Feb 12 2013 *)
%o A128992 (Magma) [(n^3-n^2)*9^n: n in [1..25]]; /* or */ I:=[0,324,13122,314928]; [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 12 2013
%Y A128992 Cf. A128796, A036289.
%K A128992 nonn,easy
%O A128992 1,2
%A A128992 _Mohammad K. Azarian_, Apr 30 2007
%E A128992 Offset corrected by _Mohammad K. Azarian_, Nov 20 2008