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 A133667 #22 Jan 02 2024 08:56:13
%S A133667 1,5,-20,-145,355,3980,-4895,-104395,17980,2627855,2178355,-63518020,
%T A133667 -117976895,1469973605,4419395980,-32329944145,-142814843645,
%U A133667 665433759980,4235804851105,-12400039148395,-118295160426020,191705818283855
%N A133667 a(n) = a(n-1) - 25*a(n-2), a(0)=1, a(1)=5.
%H A133667 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1,-25).
%F A133667 G.f.: (1+4*x)/(1-x+25*x^2).
%F A133667 a(n) = Sum_{k=0..n} A133607(n,k)*5^k. - _Philippe Deléham_, Dec 29 2007
%t A133667 LinearRecurrence[{1,-25},{1, 5}, 22] (* _Georg Fischer_, May 02 2019 *)
%o A133667 (PARI) Vec((1+4*x)/(1-x+25*x^2) + O(x^30)) \\ _Michel Marcus_, May 02 2019
%Y A133667 Cf. A133607.
%K A133667 easy,sign
%O A133667 0,2
%A A133667 _Philippe Deléham_, Dec 28 2007
%E A133667 a(10) corrected by _Georg Fischer_, May 02 2019