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 A000825 #18 Dec 30 2017 14:44:23
%S A000825 1,1,3,8,57,256,2763,17408,250737,2031616,36581523,362283008,
%T A000825 7828053417,91620376576,2309644635483,31191159799808,898621108880097,
%U A000825 13753735117275136,445777636063460643,7625476699018231808
%N A000825 Expansion of cos x (1 + sin x ) /cos 2x.
%H A000825 R. J. Mathar, <a href="/A000825/b000825.txt">Table of n, a(n) for n = 0..200</a>
%F A000825 a(n) ~ n! * (sqrt(2) + 1 + (sqrt(2)-1)*(-1)^n) * 4^n / Pi^(n+1). - _Vaclav Kotesovec_, Jun 01 2015
%t A000825 With[{nn=20},CoefficientList[Series[Cos[x] (1+Sin[x])/Cos[2x],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Nov 08 2013 *)
%Y A000825 Cf. A000828, A000831.
%Y A000825 Bisections are A000281 and (1/2) * A012393.
%K A000825 nonn
%O A000825 0,3
%A A000825 _N. J. A. Sloane_