%I #4 Feb 24 2012 12:50:42
%S 1,-1,1,-1,449,-31681,3077185,-445157441,87981830785,-22627780368001,
%T 7353703042163585,-2948527179059299201,1429774747400938052161,
%U -824792570907860638058561,558247886671770078618138049
%N sech(tan(arcsinh(x)))=1-1/2!*x^2+1/4!*x^4-1/6!*x^6+449/8!*x^8...
%K sign
%O 0,5
%A Patrick Demichel (patrick.demichel(AT)hp.com)
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