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 A009433 #21 Sep 06 2023 04:32:03
%S A009433 0,1,-1,-1,0,-11,15,27,-504,11817,-94185,1226455,-12442056,155936221,
%T A009433 -1995562569,27870901107,-423463160400,6793396567633,-117302680146033,
%U A009433 2130615128588591,-40960288523646320,827190717641773765
%N A009433 Expansion of e.g.f. log(1+x)/cosh(tan(x)).
%H A009433 G. C. Greubel, <a href="/A009433/b009433.txt">Table of n, a(n) for n = 0..448</a>
%F A009433 a(n) ~ (n-1)! * (-1)^(n+1) / cosh(tan(1)). - _Vaclav Kotesovec_, Jan 23 2015
%t A009433 With[{m=25}, CoefficientList[Series[Log[1+x]/Cosh[Tan[x]], {x,0,m}], x]*Range[0, m]!] (* modified by _G. C. Greubel_, Sep 06 2023 *)
%t A009433 CoefficientList[Series[Log[1 + x]*Sech[Tan[x]], {x, 0, 20}], x] * Range[0, 20]! (* _Vaclav Kotesovec_, Jan 23 2015 *)
%o A009433 (Magma)
%o A009433 R<x>:=PowerSeriesRing(Rationals(), 30);
%o A009433 [0] cat Coefficients(R!(Laplace( Log(1+x)/Cosh(Tan(x)) ))); // _G. C. Greubel_, Sep 06 2023
%o A009433 (SageMath)
%o A009433 def A009433_list(prec):
%o A009433 P.<x> = PowerSeriesRing(QQ, prec)
%o A009433 return P( log(1+x)/cosh(tan(x)) ).egf_to_ogf().list()
%o A009433 A009433_list(40) # _G. C. Greubel_, Sep 06 2023
%o A009433 (PARI) my(x='x+O('x^30)); concat([0],Vec(serlaplace(log(1+x)/cosh(tan(x))))) \\ _Joerg Arndt_, Sep 06 2023
%Y A009433 Cf. A009405 - A009420, A009422 - A009432, A009434 - A009439.
%K A009433 sign,easy
%O A009433 0,6
%A A009433 _R. H. Hardin_
%E A009433 Extended with signs by _Olivier Gérard_, Mar 15 1997