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 A083294 #16 Sep 08 2022 08:45:10
%S A083294 1,-1,17,-145,1313,-11809,106289,-956593,8609345,-77484097,697356881,
%T A083294 -6276211921,56485907297,-508373165665,4575358490993,-41178226418929,
%U A083294 370604037770369,-3335436339933313,30018927059399825,-270170343534598417,2431533091811385761
%N A083294 a(n) = (4 + (-9)^n)/5.
%H A083294 Vincenzo Librandi, <a href="/A083294/b083294.txt">Table of n, a(n) for n = 0..300</a>
%H A083294 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-8,9).
%F A083294 a(n) = (4 + (-9)^n)/5.
%F A083294 G.f.: (1+7*x)/((1-x)*(1+9*x)).
%F A083294 E.g.f.: (4*exp(x) + exp(-9*x))/5.
%t A083294 (4+(-9)^Range[0,20])/5 (* or *) LinearRecurrence[{-8,9},{1,-1},30] (* _Harvey P. Dale_, Sep 25 2021 *)
%o A083294 (Magma) [(4+(-9)^n)/5: n in [0..30]]; // _Vincenzo Librandi_, Jun 08 2011
%Y A083294 Cf. A083295.
%K A083294 easy,sign
%O A083294 0,3
%A A083294 _Paul Barry_, Apr 24 2003