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 A024281 #9 Apr 02 2017 15:35:13
%S A024281 0,1,8,76,-2752,-553904,-77878912,-11370511424,-1778864822272,
%T A024281 -282582967817984,-36606453394757632,2075368674171759616,
%U A024281 5791517230149348343808,4398620127304280971595776
%N A024281 Expansion of sin(tan(x)^2)/2.
%t A024281 With[{nn=30},Take[CoefficientList[Series[Sin[Tan[x]^2]/2,{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Feb 12 2016 *)
%Y A024281 Cf. A009518.
%K A024281 sign
%O A024281 0,3
%A A024281 _R. H. Hardin_
%E A024281 Extended with signs Mar 1997
%E A024281 Prior Mathematica program replaced by _Harvey P. Dale_, Feb 12 2016