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Expansion of e.g.f. cos(tan(x)/cosh(x)), even terms only.
1

%I #14 Jul 24 2018 21:23:49

%S 1,-1,5,-157,3817,-257049,15886125,-1844058101,218349214545,

%T -38729647296945,7468216325125589,-1882371895493492429,

%U 533348579359954590009,-181834605583994802568393

%N Expansion of e.g.f. cos(tan(x)/cosh(x)), even terms only.

%H G. C. Greubel, <a href="/A009082/b009082.txt">Table of n, a(n) for n = 0..239</a>

%t With[{nmax = 60}, CoefficientList[Series[Cos[Tan[x]/Cosh[x]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* _G. C. Greubel_, Jul 24 2018 *)

%o (PARI) x='x+O('x^60); v=Vec(serlaplace(cos(tan(x)/cosh(x)))); vector(#v\2,n,v[2*n-1]) \\ _G. C. Greubel_, Jul 24 2018

%K sign

%O 0,3

%A _R. H. Hardin_

%E Extended with signs by _Olivier GĂ©rard_, Mar 15 1997