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 A009434 #22 Sep 06 2023 04:32:06
%S A009434 0,1,-1,-1,0,69,-225,-1653,3976,187401,-965385,-14516745,61266744,
%T A009434 3032650893,-21187300953,-491788726653,2947006495920,166337505847057,
%U A009434 -1463633608132017,-46261934493321105,358635306874354320
%N A009434 Expansion of e.g.f: log(1+x)/cosh(tanh(x)).
%H A009434 Vincenzo Librandi, <a href="/A009434/b009434.txt">Table of n, a(n) for n = 0..200</a>
%t A009434 With[{nn=20},CoefficientList[Series[Log[1+x]/Cosh[Tanh[x]],{x,0,nn}], x] Range[0,nn]!] (* _Harvey P. Dale_, Jun 19 2013 *)
%o A009434 (Magma)
%o A009434 R<x>:=PowerSeriesRing(Rationals(), 30);
%o A009434 [0] cat Coefficients(R!(Laplace( Log(1+x)/Cosh(Tanh(x)) ))); // _G. C. Greubel_, Sep 06 2023
%o A009434 (SageMath)
%o A009434 def A009434_list(prec):
%o A009434 P.<x> = PowerSeriesRing(QQ, prec)
%o A009434 return P( log(1+x)/cosh(tanh(x)) ).egf_to_ogf().list()
%o A009434 A009434_list(40) # _G. C. Greubel_, Sep 06 2023
%o A009434 (PARI) my(x='x+O('x^30)); concat([0],Vec(serlaplace(log(1+x)/cosh(tanh(x))))) \\ _Joerg Arndt_, Sep 06 2023
%Y A009434 Cf. A009405 - A009420, A009422 - A009433, A009435 - A009439.
%K A009434 sign,easy
%O A009434 0,6
%A A009434 _R. H. Hardin_
%E A009434 Extended with signs by _Olivier Gérard_, Mar 15 1997
%E A009434 Definition clarified and prior Mathematica program replaced by _Harvey P. Dale_, Jun 19 2013