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 A003719 M3996 #22 Nov 04 2019 17:45:54
%S A003719 1,5,41,685,19921,887765,56126201,4776869245,526589630881,
%T A003719 72989204937125,12424192360405961,2547879762929443405,
%U A003719 619570064016825283441,176273806836039238900085,58010159408189457446855321,21864887814006548202566779165
%N A003719 Expansion of tan(x)*cosh(x).
%D A003719 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%F A003719 a(n) = Sum_{k>=0} binomial(2n+1, 2k)*A000111(2n+1-2k). - _Philippe Deléham_, Aug 27 2005
%F A003719 a(n) ~ cosh(Pi/2) * (2*n+1)! * 2^(2*n+3) / Pi^(2*n+2). - _Vaclav Kotesovec_, Feb 16 2015
%t A003719 nn = 20; Table[(CoefficientList[Series[Cosh[x]*Tan[x], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* _Vaclav Kotesovec_, Feb 16 2015 *)
%Y A003719 Bisection of A009739 and (apparently) A062272.
%K A003719 nonn
%O A003719 0,2
%A A003719 _R. H. Hardin_
%E A003719 Extended and formatted Mar 15 1997 by _Olivier Gérard_
%E A003719 Prior Mathematica program deleted by _Harvey P. Dale_, Nov 04 2019