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 A121607 #13 Sep 08 2022 08:45:27
%S A121607 6,90,810,5508,31590,161838,765450,3411720,14526054,59639490,
%T A121607 237731274,924707340,3523453830,13191428502,48642794730,177008116752,
%U A121607 636661003590,2266409860650,7994034370026,27964010896020,97092998430246
%N A121607 (n^3+n)*3^n.
%H A121607 Vincenzo Librandi, <a href="/A121607/b121607.txt">Table of n, a(n) for n = 1..1000</a>
%F A121607 G.f.: 6*x*(1 + 3*x + 9*x^2)/(1 - 3*x)^4. - _Vincenzo Librandi_, Feb 22 2013
%t A121607 Table[(n^3 + n)*3^n, {n, 30}] (* or *) CoefficientList[Series[6 (1 + 3 x + 9 x^2)/(1 - 3 x)^4, {x, 0, 30}], x] (* _Vincenzo Librandi_, Feb 22 2013 *)
%o A121607 (Magma) [(n^3 + n)*3^n: n in [1..30]]; // _Vincenzo Librandi_, Feb 22 2013
%Y A121607 Cf. A128796, A128960, A128985, A129002.
%K A121607 nonn,easy
%O A121607 1,1
%A A121607 _Mohammad K. Azarian_, May 02 2007