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 A147722 #24 Dec 31 2023 11:35:49
%S A147722 1,2,8,36,164,748,3412,15564,70996,323852,1477268,6738636,30738644,
%T A147722 140215948,639602452,2917580364,13308696916,60708323852,276924225428,
%U A147722 1263204479436,5762173946324,26284460772748,119897955971092,546920858309964,2494808379607636,11380200181418252
%N A147722 Row sums of Riordan array ((1-3x)/(1-4x+x^2), x(1-x)/(1-4x+x^2)).
%C A147722 Row sums of A147721.
%C A147722 Hankel transform of a(n) is [1,4,0,0,0,0,0,0,...]. [_Philippe Deléham_, Dec 03 2008]
%H A147722 Indranil Ghosh, <a href="/A147722/b147722.txt">Table of n, a(n) for n = 0..200</a>
%H A147722 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,-2).
%F A147722 G.f.: (1-3x)/(1-5x+2x^2).
%F A147722 a(n) = 5*a(n-1)-2*a(n-2), a(0)=1, a(1)=2. [_Philippe Deléham_, Nov 13 2008]
%t A147722 CoefficientList[Series[(1 - 3x)/(1 - 5x + 2x^2) , {x, 0, 21}], x] (* _Indranil Ghosh_, Mar 10 2017 *)
%t A147722 LinearRecurrence[{5,-2},{1,2},30] (* _Harvey P. Dale_, Aug 26 2021 *)
%o A147722 (PARI) Vec((1 - 3*x)/(1 - 5*x + 2*x^2) + O(x^22)) \\ _Indranil Ghosh_, Mar 10 2017
%K A147722 easy,nonn
%O A147722 0,2
%A A147722 _Paul Barry_, Nov 11 2008