A012465 - OEIS

%I #8 Nov 28 2016 18:55:40

%S 1,0,12,-480,31248,-3160320,462297792,-92467554816,24237361774848,

%T -8058187934539776,3312017870282345472,-1648428171351870627840,

%U 976764310209146448384000,-679332936418413117235200000

%N cosh(arctan(x)*arctan(x))=1+12/4!*x^4-480/6!*x^6+31248/8!*x^8...

%t nn = 20; Table[(CoefficientList[Series[Cosh[ArcTan[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* _Vaclav Kotesovec_, Feb 08 2015 *)

%K sign

%O 0,3

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