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 A155181 #24 Jan 19 2024 09:10:24
%S A155181 1,4,20,104,540,2804,14560,75604,392580,2038504,10585100,54964004,
%T A155181 285405120,1481989604,7695353140,39958755304,207489129660,
%U A155181 1077404403604,5594511147680,29049960142004,150844311857700,783271519430504
%N A155181 a(n)=5*a(n-1)+a(n-2), n>2 ; a(0)=1, a(1)=4, a(2)=20 .
%H A155181 Paolo Xausa, <a href="/A155181/b155181.txt">Table of n, a(n) for n = 0..1000</a>
%H A155181 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,1).
%F A155181 G.f.: (1-x-x^2)/(1-5*x-x^2).
%F A155181 a(n) = Sum_{k=0..n} A155161(n,k)*4^k. - _Philippe Deléham_, Feb 08 2012
%t A155181 LinearRecurrence[{5, 1}, {1, 4, 20}, 25] (* _Paolo Xausa_, Jan 19 2024 *)
%Y A155181 Cf. A155161.
%K A155181 nonn,easy
%O A155181 0,2
%A A155181 _Philippe Deléham_, Jan 21 2009