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 A009429 #22 Apr 01 2017 14:15:08
%S A009429 0,1,-1,5,-12,69,-285,2001,-12208,104073,-854865,8723549,-90552396,
%T A009429 1088372557,-13647385661,190057979177,-2787246189120,44285819490065,
%U A009429 -742019231348865,13267464006201781,-249642268776311020
%N A009429 E.g.f. log(1+x)/cos(x).
%H A009429 Vincenzo Librandi, <a href="/A009429/b009429.txt">Table of n, a(n) for n = 0..200</a>
%F A009429 a(n) ~ (n-1)! * (-1)^(n+1) / cos(1). - _Vaclav Kotesovec_, Jan 23 2015
%e A009429 log(1+x)/cos(x) = 0 + x - 1/2*x^2 + 5/6*x^3 - 1/2*x^4 + 23/40*x^5 -+ ...
%t A009429 With[{nn=30},CoefficientList[Series[Log[1+x]/Cos[x],{x,0,nn}], x] Range[0,nn]!] (* _Harvey P. Dale_, Jan 26 2013 *)
%K A009429 sign,easy
%O A009429 0,4
%A A009429 _R. H. Hardin_
%E A009429 Extended with signs by _Olivier Gérard_, Mar 15 1997