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 A128797 #21 Sep 08 2022 08:45:30
%S A128797 0,0,18,162,972,4860,21870,91854,367416,1417176,5314410,19486170,
%T A128797 70150212,248714388,870500358,3013270470,10331213040,35126124336,
%U A128797 118550669634,397493421714,1324978072380,4393348345260,14498049539358
%N A128797 (n^2-n)*3^n.
%H A128797 Vincenzo Librandi, <a href="/A128797/b128797.txt">Table of n, a(n) for n = 0..1000</a>
%H A128797 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (9,-27,27).
%F A128797 G.f.: 18*x^2/(1-3*x)^3. - _Vincenzo Librandi_, Feb 10 2013
%F A128797 a(n) = 18*A027472(n+1). - _R. J. Mathar_, Apr 26 2015
%t A128797 CoefficientList[Series[18 x^2/(1 - 3 x)^3, {x, 0, 30}], x] (* _Vincenzo Librandi_, Feb 10 2013 *)
%t A128797 LinearRecurrence[{9,-27,27},{0,0,18},40] (* _Harvey P. Dale_, Dec 15 2014 *)
%o A128797 (Magma) [(n^2-n)*3^n: n in [0..25]]; // _Vincenzo Librandi_, Feb 10 2013
%Y A128797 Cf. A036289, A007758.
%K A128797 nonn,easy
%O A128797 0,3
%A A128797 _Mohammad K. Azarian_, Apr 07 2007