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 A096720 #9 Nov 21 2016 04:25:05
%S A096720 1,6,120,5040,362880,13305600,2075673600,435891456000,13173608448000,
%T A096720 13516122267648000,5676771352412160000,2872446304320552960000,
%U A096720 14243535393325056000000,241974876675963381350400000,949196134593634133606400000,20303305318957834117840896000000,4288058083363894565687997235200000
%N A096720 Denominators of terms in series expansion of arctan(arcsin(x)).
%H A096720 G. C. Greubel, <a href="/A096720/b096720.txt">Table of n, a(n) for n = 0..200</a>
%e A096720 arctan(arcsin(x)) = x - 1/6*x^3 + 13/120*x^5 - 173/5040*x^7 + 12409/362880*x^9 - 123379/13305600*x^11 + ...
%t A096720 Denominator[Take[CoefficientList[Series[ArcTan[ArcSin[x]],{x,0,40}],x] ,{2,-1,2}]] (* _Harvey P. Dale_, May 04 2013 *)
%Y A096720 Cf. A096719, A096718, A096664, A096671, A096712, A096716, A045688, A045689.
%K A096720 nonn,frac
%O A096720 0,2
%A A096720 _N. J. A. Sloane_, Aug 15 2004