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 A098484 #12 Jan 30 2020 21:29:15
%S A098484 1,1,1,1,7,19,37,61,145,397,979,2107,4591,10915,26857,63649,146347,
%T A098484 339751,808885,1936717,4588705,10803133,25559287,60893551,145231309,
%U A098484 345462145,821110051,1955736379,4668132067,11146642903,26605635949
%N A098484 Expansion of 1/sqrt((1-x)^2-12x^4).
%C A098484 1/sqrt((1-x)^2-4rx^4) expands to sum{k=0..floor(n/2), binomial(n-2k,k)binomial(n-3k,k)r^k}.
%H A098484 Vincenzo Librandi, <a href="/A098484/b098484.txt">Table of n, a(n) for n = 0..200</a>
%F A098484 a(n)=sum{k=0..floor(n/2), binomial(n-2k, k)binomial(n-3k, k)3^k}.
%F A098484 D-finite with recurrence: n*a(n) = (2*n-1)*a(n-1) - (n-1)*a(n-2) + 12*(n-2)*a(n-4). - _Vaclav Kotesovec_, Jun 23 2014
%F A098484 a(n) ~ sqrt(3) * (1+sqrt(1+8*sqrt(3)))^n / (sqrt(49+10*sqrt(3)-sqrt(397+884*sqrt(3))) * sqrt(Pi*n) * 2^(n-1)). - _Vaclav Kotesovec_, Jun 23 2014
%t A098484 CoefficientList[Series[1/Sqrt[(1-x)^2-12*x^4], {x, 0, 20}], x] (* _Vaclav Kotesovec_, Jun 23 2014 *)
%Y A098484 Cf. A098481, A098482, A098483.
%K A098484 easy,nonn
%O A098484 0,5
%A A098484 _Paul Barry_, Sep 10 2004