A013138 - OEIS

%I #6 Sep 21 2024 17:12:56

%S 1,-4,16,-448,14592,-705536,65245184,-5385535488,910402060288,

%T -124371776831488,30930578556583936,-6638266678020931584,

%U 2186545615284171964416,-694382737827711997181952

%N cos(tanh(x)+tan(x))=1-4/2!*x^2+16/4!*x^4-448/6!*x^6+14592/8!*x^8...

%t With[{nn=30},Take[CoefficientList[Series[Cos[Tanh[x]+Tan[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Sep 21 2024 *)

%K sign

%O 0,2

%A Patrick Demichel (patrick.demichel(AT)hp.com)