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 A128801 #27 Sep 08 2022 08:45:30
%S A128801 0,98,2058,28812,336140,3529470,34588806,322828856,2905459704,
%T A128801 25422772410,217505941730,1827049910532,15114685623492,
%U A128801 123436599258518,996987917088030,7975903336704240,63275499804520304,498294560960597394
%N A128801 a(n) = n*(n-1)*7^n.
%H A128801 Vincenzo Librandi, <a href="/A128801/b128801.txt">Table of n, a(n) for n = 1..1000</a>
%H A128801 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (21,-147,343).
%F A128801 G.f.: 98*x^2/(1-7*x)^3. - _Emeric Deutsch_, May 04 2007
%F A128801 a(n) = 21*a(n-1) - 147*a(n-2) + 343*a(n-3). - _Vincenzo Librandi_, Feb 12 2013
%F A128801 a(n) = 98*A027474(n). - _R. J. Mathar_, Apr 26 2015
%p A128801 g:=98*x^2/(1-7*x)^3: gser:=series(g,x=0,22): seq(coeff(gser,x,n),n=1..18); # _Emeric Deutsch_, May 04 2007
%t A128801 LinearRecurrence[{21, -147, 343}, {0, 98, 2058}, 30] (* _Vincenzo Librandi_, Feb 12 2013 *)
%o A128801 (Magma) [(n^2-n)*7^n: n in [1..25]] // _Vincenzo Librandi_, Feb 12 2013
%Y A128801 Cf. A036289, A007758.
%K A128801 nonn,easy
%O A128801 1,2
%A A128801 _Mohammad K. Azarian_, Apr 07 2007