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 A009016 #13 Jul 21 2018 23:38:32
%S A009016 1,-1,-11,-61,1737,88679,2086525,-45950997,-9763133167,-705668046769,
%T A009016 -17356978593659,3823112141007763,788728947108214489,
%U A009016 82036502117747569079,1412038521698998808077
%N A009016 Expansion of E.g.f.: cos(cosh(x)*x) (even powers only).
%H A009016 G. C. Greubel, <a href="/A009016/b009016.txt">Table of n, a(n) for n = 0..250</a>
%t A009016 With[{nmax = 60}, CoefficientList[Series[Cos[x*Cosh[x]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* _G. C. Greubel_, Jul 21 2018 *)
%o A009016 (PARI) x='x+O('x^60); v=Vec(serlaplace(cos(x*cosh(x)))); vector(#v\2,n,v[2*n-1]) \\ _G. C. Greubel_, Jul 21 2018
%K A009016 sign
%O A009016 0,3
%A A009016 _R. H. Hardin_
%E A009016 Extended with signs by _Olivier Gérard_, Mar 15 1997