%I #6 Feb 27 2013 16:06:03
%S 1,0,-12,-480,-15792,387840,232592448,44951262720,4538494871808,
%T -1173690989322240,-1020600368000166912,-406075179314308669440,
%U -50036577406600515366912,87776293107173235762462720
%N sech(tan(x)*tan(x))=1-12/4!*x^4-480/6!*x^6-15792/8!*x^8...
%t With[{nn=30},Take[CoefficientList[Series[Sech[Tan[x]^2],{x,0,nn}],x] Range[ 0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Feb 27 2013 *)
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)