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 A009739 #36 May 12 2024 17:44:33
%S A009739 0,1,2,5,12,41,142,685,3192,19921,116282,887765,6219972,56126201,
%T A009739 458790022,4776869245,44625674352,526589630881,5534347077362,
%U A009739 72989204937125,852334810990332,12424192360405961,159592488559874302,2547879762929443405,35703580441464231912
%N A009739 E.g.f. tan(x)*exp(x).
%H A009739 Robert Israel, <a href="/A009739/b009739.txt">Table of n, a(n) for n = 0..484</a>
%F A009739 a(2n) = A009747(n), a(2n+1) = A003719(n).
%F A009739 E.g.f.: exp(x)*tan(x). - _Zerinvary Lajos_, Apr 05 2009
%F A009739 G.f.: 1/(x-1)/Q(0), where Q(k)= 1 - 1/x - (k+1)*(k+2)/Q(k+1); (continued fraction). - _Sergei N. Gladkovskii_, Apr 26 2013
%F A009739 G.f.: x/(1-x)/Q(0), where Q(k)= 1 - x - x^2*(k+1)*(k+2)/Q(k+1); (continued fraction). - _Sergei N. Gladkovskii_, Apr 26 2013
%F A009739 G.f.: G(0)*x/(1-x)^2, where G(k) = 1 - x^2*(k+1)*(k+2)/(x^2*(k+1)*(k+2) - (1-x)^2/G(k+1) ); (continued fraction). - _Sergei N. Gladkovskii_, Jan 23 2014
%F A009739 a(n) ~ 2^(3/2 + n)*(exp(Pi) - (-1)^n)*exp(-Pi/2 - n)*Pi^(-1/2 - n)*n^(1/2 + n). - _Robert Israel_, Sep 22 2019
%p A009739 G(x):=exp(x)*tan(x): f[0]:=G(x): for n from 1 to 54 do f[n]:=diff(f[n-1],x) od: x:=0: seq(f[n],n=0..22 ); # _Zerinvary Lajos_, Apr 05 2009
%p A009739 # Alternative:
%p A009739 S:= series(exp(x)*tan(x),x, 51):
%p A009739 seq(coeff(S,x,j)*j!,j=0..50); # _Robert Israel_, Sep 22 2019
%o A009739 (PARI) x='x+O('x^66); concat([0],Vec(serlaplace(tan(x)*exp(x)))) \\ _Joerg Arndt_, Apr 26 2013
%Y A009739 Cf. A003701.
%K A009739 nonn,easy
%O A009739 0,3
%A A009739 _R. H. Hardin_
%E A009739 Extended and signs tested by _Olivier Gérard_, Mar 15 1997