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 A081922 #18 Jan 05 2021 21:31:22
%S A081922 1,4,17,76,361,1844,10321,64348,453329,3619684,32666161,329434604,
%T A081922 3677682937,44901581716,595567550321,8505627039484,130307878338721,
%U A081922 2126927187154628,36912563369550289,677277819029706124
%N A081922 Expansion of exp(4x)/sqrt(1-x^2).
%C A081922 Binomial transform of A081921
%C A081922 Generally, if e.g.f. = exp(p*x)/sqrt(1-x^2), then a(n) ~ n^n * (exp(p)+(-1)^n*exp(-p)) / exp(n). - _Vaclav Kotesovec_, Feb 04 2014
%F A081922 E.g.f.: exp(4x)/sqrt(1-x^2).
%F A081922 D-finite with recurrence: -a(n) + 4*a(n-1) + (n-1)^2*a(n-2) - 4*(n-1)*(n-2)*a(n-3) = 0. - _R. J. Mathar_, Nov 09 2012
%F A081922 a(n) ~ n^n * (exp(4) + (-1)^n*exp(-4)) / exp(n). - _Vaclav Kotesovec_, Feb 04 2014
%t A081922 With[{nn=20},CoefficientList[Series[Exp[4x]/Sqrt[1-x^2] ,{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, May 07 2012 *)
%Y A081922 Cf. A081919, A081920, A081921.
%K A081922 easy,nonn
%O A081922 0,2
%A A081922 _Paul Barry_, Apr 01 2003