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 A009090 #16 Sep 08 2022 08:44:37
%S A009090 1,-1,0,2,4,-36,-56,944,1744,-41104,-86208,2650592,6199744,-237023424,
%T A009090 -608357504,28021573376,77889982720,-4225816615168,-12588540708864,
%U A009090 790713657219584,2503565961032704,-179579770991391744
%N A009090 Expansion of e.g.f. cos(tanh(x))/exp(x).
%H A009090 G. C. Greubel, <a href="/A009090/b009090.txt">Table of n, a(n) for n = 0..250</a>
%t A009090 With[{nmax = 30}, CoefficientList[Series[Cos[Tanh[x]]/Exp[x], {x, 0, nmax}], x]*Range[0, nmax]!] (* _G. C. Greubel_, Jul 25 2018 *)
%o A009090 (PARI) x='x+O('x^30); Vec(serlaplace(cos(tanh(x))/exp(x))) \\ _G. C. Greubel_, Jul 25 2018
%o A009090 (Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Cos(Tanh(x))/Exp(x))); [Factorial(n-1)*b[n]: n in [1..m]]; // _G. C. Greubel_, Jul 25 2018
%K A009090 sign,easy
%O A009090 0,4
%A A009090 _R. H. Hardin_
%E A009090 Extended with signs by _Olivier Gérard_, Mar 15 1997