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 A002506 #17 Oct 17 2023 05:43:35
%S A002506 8,96,3072,184320,17694720,2477260800,475634073600,119859786547200,
%T A002506 38355131695104000,15188632151261184000,7290543432605368320000,
%U A002506 4170190843450270679040000,2802368246798581896314880000
%N A002506 Denominators of coefficients of expansion of Bessel function J_2(x).
%D A002506 Bronstein-Semendjajew, Taschenbuch der Mathematik, 7th German ed. 1965, ch. 4.4.7
%H A002506 T. D. Noe, <a href="/A002506/b002506.txt">Table of n, a(n) for n = 0..50</a>
%H A002506 <a href="/index/Be#Bessel">Index entries for sequences related to Bessel functions or polynomials</a>
%F A002506 a(n) = 2^(2n+k) * n! * (n+k)! here for k=2, i.e., Bessel's J2(x).
%F A002506 a(n) - 4*n*(n+2)*a(n-1) = 0. - _R. J. Mathar_, Jun 20 2013
%e A002506 a(2) = 3072 = 64*2*24, J2(x) = x^2/8 - x^4/96 + x^6/3072 - x^8/184320 +- ...
%t A002506 Denominator[Take[CoefficientList[Series[BesselJ[2,x],{x,0,30}],x],{3,-1,2}]] (* _Harvey P. Dale_, Sep 21 2013 *)
%Y A002506 J0: A002454, J1: A002474, J3: A014401.
%K A002506 nonn
%O A002506 0,1
%A A002506 _N. J. A. Sloane_
%E A002506 Previous Mathematica program corrected by _Harvey P. Dale_, Sep 21 2013