A009086 - OEIS

%I #18 Jul 25 2018 08:16:38

%S 1,-1,1,47,449,-18209,-1441087,-41192817,2660018305,460752070079,

%T 21450325749889,-1057483104728337,760394598152560705,

%U 506532040802152000159,99674104328764912612673

%N Expansion of e.g.f. cos(tanh(tan(x))), even powers only.

%H G. C. Greubel, <a href="/A009086/b009086.txt">Table of n, a(n) for n = 0..242</a>

%p seq(coeff(series(factorial(n)*cos(tanh(tan(x))), x,n+1),x,n),n=0..30,2); # _Muniru A Asiru_, Jul 25 2018

%t With[{nmax = 60}, CoefficientList[Series[Cos[Tanh[Tan[x]]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* _G. C. Greubel_, Jul 25 2018 *)

%o (PARI) x='x+O('x^50); v=Vec(serlaplace(cos(tanh(tan(x))))); vector(#v\2,n,v[2*n-1]) \\ _G. C. Greubel_, Jul 25 2018

%K sign

%O 0,4

%A _R. H. Hardin_

%E Extended with signs by _Olivier Gérard_, Mar 15 1997