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 A098481 #23 Jan 30 2020 21:29:15
%S A098481 1,1,1,7,19,37,115,361,937,2599,7777,22195,62701,182647,531829,
%T A098481 1534903,4461571,13034917,38015899,110994193,325011151,952442557,
%U A098481 2792471239,8198275933,24093817531,70852613041,208516575043,614145137137
%N A098481 Expansion of 1/sqrt((1-x)^2 - 12*x^3).
%C A098481 1/sqrt((1-x)^2 - 4*r*x^3) expands to Sum_{k=0..floor(n/2)} binomial(n-k, k)*binomial(n-2k, k)*r^k.
%H A098481 G. C. Greubel and Vincenzo Librandi, <a href="/A098481/b098481.txt">Table of n, a(n) for n = 0..1000</a>(terms 0..200 from Vincenzo Librandi)
%F A098481 a(n) = Sum_{k=0..floor(n/2)} binomial(n-k, k)*binomial(n-2k, k)*3^k.
%F A098481 D-finite with recurrence: n*a(n) = (2*n-1)*a(n-1) - (n-1)*a(n-2) + 6*(2*n-3)*a(n-3). - _Vaclav Kotesovec_, Jun 23 2014
%F A098481 a(n) ~ 3^(n+1) / (4*sqrt(Pi*n)). - _Vaclav Kotesovec_, Jun 23 2014
%t A098481 CoefficientList[Series[1/Sqrt[(1-x)^2-12x^3],{x,0,40}],x] (* _Harvey P. Dale_, Jun 02 2011 *)
%o A098481 (PARI) Vec(1/sqrt((1-x)^2 - 12*x^3) + O(x^50)) \\ _G. C. Greubel_, Jan 30 2017
%Y A098481 Cf. A098479, A098480.
%K A098481 easy,nonn
%O A098481 0,4
%A A098481 _Paul Barry_, Sep 10 2004