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

%I #19 Jan 26 2024 04:59:53

%S 1,-1,-19,-397,-7943,64551,43466469,7570028763,1224976528753,

%T 203222727578703,33945910273599581,5001827577751516739,

%U 201232322297192328041,-395596937210124802877833

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

%H G. C. Greubel, <a href="/A009075/b009075.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^50); 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