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 A166036 #19 Feb 18 2018 02:44:33
%S A166036 1,-4,24,-104,584,-2664,14344,-67624,354504,-1706984,8797064,
%T A166036 -42936744,218878024,-1077612904,5455173384,-27007431464,136110899144,
%U A166036 -676259528424,3398477511304,-16923668079784
%N A166036 a(n) = (4^n+8*(-5)^n)/9.
%H A166036 Harvey P. Dale, <a href="/A166036/b166036.txt">Table of n, a(n) for n = 0..1000</a>
%H A166036 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-1,20).
%F A166036 a(n) = -a(n-1) + 20*a(n-2), a(0) = 1, a(1) = -4, for n>1.
%F A166036 a(n) = Sum_{k=0..n} A112555(n,k)*(-5)^k.
%F A166036 G.f.: (1-3x)/(1+x-20x^2).
%F A166036 E.g.f.: (1/9)*(exp(4*x) + 8*exp(-5*x)). - _G. C. Greubel_, Apr 24 2016
%t A166036 Table[(4^n+8(-5)^n)/9,{n,0,30}] (* or *) LinearRecurrence[{-1,20},{1,-4},30] (* _Harvey P. Dale_, Mar 05 2016 *)
%o A166036 (PARI) vector(100, n, n--; (4^n+8*(-5)^n)/9) \\ _Altug Alkan_, Apr 24 2016
%Y A166036 Cf. A077925, A091004, A166035.
%K A166036 easy,sign
%O A166036 0,2
%A A166036 _Philippe Deléham_, Oct 05 2009