A009186 - OEIS

%I #18 Dec 10 2024 08:58:33

%S 1,-1,2,-6,16,-72,328,-1848,11712,-81088,638720,-5318016,49459840,

%T -483162240,5159926528,-57865303296,697030680576,-8815813734400,

%U 118233272496128,-1662921003208704,24578235697610752,-380141599264751616,6139851821419921408

%N Expansion of e.g.f.: cosh(x)/exp(tan(x)).

%H Vincenzo Librandi, <a href="/A009186/b009186.txt">Table of n, a(n) for n = 0..200</a>

%p a:= n-> n! * coeff (series (cosh(x)/exp(tan(x)), x, n+1), x, n):

%p seq (a(n), n=0..30);  # _Alois P. Heinz_, May 16 2012

%t With[{nn=30},CoefficientList[Series[Cosh[x]/Exp[Tan[x]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, May 16 2012 *)

%K sign,easy

%O 0,3

%A _R. H. Hardin_

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

%E Definition clarified by _Harvey P. Dale_, May 16 2012