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 A009435 #22 Sep 06 2023 04:32:10
%S A009435 0,1,-1,-1,0,29,-105,139,-2072,31737,-247545,1824151,-22456104,
%T A009435 313750293,-3929185169,51584719523,-793292190480,13137192234225,
%U A009435 -221862616530705,3947317975733039,-75492532592047280,1522475446731094285
%N A009435 Expansion of e.g.f.: log(1+x)/cosh(x).
%H A009435 G. C. Greubel, <a href="/A009435/b009435.txt">Table of n, a(n) for n = 0..449</a>
%F A009435 a(n) ~ (-1)^(n+1) * (n-1)! / cosh(1). - _Vaclav Kotesovec_, Oct 01 2014
%t A009435 With[{nn=30},CoefficientList[Series[Log[1+x]/Cosh[x],{x,0,nn}],x] Range[ 0,nn]!] (* _Harvey P. Dale_, Oct 01 2014 *)
%o A009435 (Magma)
%o A009435 R<x>:=PowerSeriesRing(Rationals(), 30);
%o A009435 [0] cat Coefficients(R!(Laplace( Log(1+x)/Cosh(x) ))); // _G. C. Greubel_, Sep 06 2023
%o A009435 (SageMath)
%o A009435 def A009435_list(prec):
%o A009435 P.<x> = PowerSeriesRing(QQ, prec)
%o A009435 return P( log(1+x)/cosh(x) ).egf_to_ogf().list()
%o A009435 A009435_list(40) # _G. C. Greubel_, Sep 06 2023
%o A009435 (PARI) my(x='x+O('x^30)); concat([0],Vec(serlaplace(log(1+x)/cosh(x)))) \\ _Joerg Arndt_, Sep 06 2023
%Y A009435 Cf. A009405 - A009420, A009422 - A009434, A009436 - A009439.
%K A009435 sign,easy
%O A009435 0,6
%A A009435 _R. H. Hardin_
%E A009435 Extended with signs by _Olivier Gérard_, Mar 15 1997
%E A009435 Definition clarified and prior Mathematica program replaced by _Harvey P. Dale_, Oct 01 2014