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 A113180 #16 Jan 30 2020 21:29:15
%S A113180 1,2,4,8,20,56,160,448,1240,3440,9632,27200,77216,219840,627200,
%T A113180 1793024,5136480,14743232,42390400,122064640,351951232,1015990528,
%U A113180 2936079360,8493340672,24591589120,71262291456,206666232832,599778166784
%N A113180 Expansion of 1/sqrt((1-2*x)^2-8*x^4).
%C A113180 In general, 1/sqrt((1-a*x)^2-4*b*x^4) expands to Sum_{k=0..floor(n/2)} C(n-2k,k)*C(n-3k,k)*b^k*a^(n-4k).
%H A113180 G. C. Greubel, <a href="/A113180/b113180.txt">Table of n, a(n) for n = 0..1000</a> (terms 0..200 from Vincenzo Librandi)
%F A113180 a(n) = Sum_{k=0..floor(n/2)} C(n-2k,k)*C(n-3k,k)*2^(n-3k).
%F A113180 D-finite with recurrence: n*a(n) = 2*(2*n-1)*a(n-1) - 4*(n-1)*a(n-2) + 8*(n-2)*a(n-4). - _Vaclav Kotesovec_, Jun 23 2014
%F A113180 a(n) ~ (1+sqrt(1+2*sqrt(2)))^n / (sqrt(6+5*sqrt(2)-sqrt(70+56*sqrt(2))) * sqrt(Pi*n)). - _Vaclav Kotesovec_, Jun 23 2014
%t A113180 CoefficientList[Series[1/Sqrt[(1-2*x)^2-8*x^4], {x, 0, 20}], x] (* _Vaclav Kotesovec_, Jun 23 2014 *)
%o A113180 (PARI) x='x+O('x^50); Vec(1/sqrt((1-2*x)^2 - 8*x^4)) \\ _G. C. Greubel_, Mar 17 2017
%Y A113180 Cf. A098482, A113179.
%K A113180 easy,nonn
%O A113180 0,2
%A A113180 _Paul Barry_, Oct 16 2005