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 A098460 #24 May 10 2020 19:33:50
%S A098460 1,1,5,33,321,3945,59445,1056825,21677985,503799345,13084021125,
%T A098460 375524312625,11803392302625,403235809601625,14876913457531125,
%U A098460 589498927632239625,24969077812488434625,1125803018759825030625
%N A098460 Expansion of e.g.f. 1/sqrt(1-2x-2x^2).
%F A098460 a(n) = (n!/2^n)*A084609(n);
%F A098460 a(n) = (n!/2^n) * Sum_{k=0..floor(n/2)} binomial(n,k)*binomial(2(n-k),n)*2^k;
%F A098460 a(n) = n! * Sum_{k=0..floor(n/2)} binomial(n,k)*binomial(2(n-k),n)*2^(k-n).
%F A098460 D-finite with recurrence: a(n) +(1-2*n)*a(n-1) -2*(n-1)^2*a(n-2)=0. - _R. J. Mathar_, Nov 15 2011
%F A098460 a(n) ~ 2^(n+1/2)*n^n/(sqrt(3-sqrt(3))*exp(n)*(sqrt(3)-1)^n). - _Vaclav Kotesovec_, Jun 26 2013
%t A098460 CoefficientList[Series[1/Sqrt[1-2*x-2*x^2], {x, 0, 20}], x]* Range[0, 20]! (* _Vaclav Kotesovec_, Jun 26 2013 *)
%o A098460 (PARI) my(x='x+O('x^25)); Vec(serlaplace(1/sqrt(1-2*x-2*x^2))) \\ _Michel Marcus_, May 10 2020
%Y A098460 Cf. A012244.
%K A098460 easy,nonn
%O A098460 0,3
%A A098460 _Paul Barry_, Sep 08 2004