A012467 - OEIS

%I #10 Nov 21 2013 12:46:01

%S 1,0,-12,480,-21168,741120,61942848,-29951061504,8015861467392,

%T -1745546459848704,215844160641143808,91751419512905687040,

%U -109687232118939992862720,71900040403600384794624000

%N sech(arctan(x)^2) = 1 - 12/4!*x^4 + 480/6!*x^6 - 21168/8!*x^8 + ...

%t With[{nn=30},Take[CoefficientList[Series[Sech[ArcTan[x]^2],{x,0,nn}] ,x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Apr 30 2012 *)

%K sign

%O 0,3

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

%E Definition corrected by Harvey P. Dale, Apr 30 2012