The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #4 Feb 24 2012 12:51:09
%S 1,1,5,205,2473,475385,-2814227,5900398725,-532397600303,
%T 273302104270705,-68724093821987755,35776180280496600509,
%U -16339748046588020242311,10552119508350355540652905
%N cosh(sec(x)*arctan(x))=1+1/2!*x^2+5/4!*x^4+205/6!*x^6+2473/8!*x^8...
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)