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 A198397 #25 Sep 10 2024 20:00:09
%S A198397 1,0,35,322,2373,16772,117607,823494,5764745,40353544,282475179,
%T A198397 1977326666,13841287117,96889010316,678223072751,4747561509838,
%U A198397 33232930569489,232630513987088,1628413597910323,11398895185373010,79792266297611861,558545864083283860,3909821048582987895
%N A198397 a(n) = 7^n - 7*n.
%H A198397 Vincenzo Librandi, <a href="/A198397/b198397.txt">Table of n, a(n) for n = 0..1000</a>
%H A198397 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (9,-15,7).
%F A198397 a(n) = 9*a(n-1) - 15*a(n-2) + 7*a(n-3) for n > 2.
%F A198397 G.f.: (1 - 9*x + 50*x^2)/((1 - 7*x)*(1 -x)^2). - _Vincenzo Librandi_, Jan 04 2013
%F A198397 E.g.f.: exp(x)*(exp(6*x) - 7*x). - _Elmo R. Oliveira_, Sep 10 2024
%t A198397 CoefficientList[Series[(1 - 9*x + 50*x^2)/((1 - 7*x)*(1 -x)^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 04 2013 *)
%o A198397 (Magma) [7^n-7*n: n in [0..25]];
%o A198397 (PARI) a(n)=7^n-7*n \\ _Charles R Greathouse IV_, Jul 06 2017
%Y A198397 Cf. A005803, A107583, A107584, A107585.
%K A198397 nonn,easy
%O A198397 0,3
%A A198397 _Vincenzo Librandi_, Oct 26 2011