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 A046981 #13 Feb 14 2014 21:07:15
%S A046981 1,1,1,3,6,30,1,630,2520,22680,1,1247400,7484400,97297200,1,
%T A046981 10216206000,81729648000,1389404016000,1,237588086736000,
%U A046981 2375880867360000,49893498214560000,1,12623055048283680000,151476660579404160000,3786916514485104000000
%N A046981 Denominators of Taylor series for exp(x)*cos(x).
%D A046981 G. W. Caunt, Infinitesimal Calculus, Oxford Univ. Press, 1914, p. 477.
%H A046981 T. D. Noe, <a href="/A046981/b046981.txt">Table of n, a(n) for n=0..100</a>
%F A046981 a(4n+2) = 1, a(n) = n!/2^[n/2].
%e A046981 1+1*x-1/3*x^3-1/6*x^4-1/30*x^5+1/630*x^7+1/2520*x^8+1/22680*x^9-...
%t A046981 Denominator/@CoefficientList[Series[Exp[x]Cos[x],{x,0,30}],x] (* _Harvey P. Dale_, Jun 28 2011 *)
%Y A046981 Cf. A046980, A046979, A052277, A007019, A007415, A009775, A092820.
%Y A046981 Absolute values are essentially the same as A007452.
%K A046981 nonn,frac,easy,nice
%O A046981 0,4
%A A046981 _N. J. A. Sloane_