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%I #17 Apr 02 2017 15:34:27
%S 0,1,-6,176,-8176,691456,-86186496,15358324736,-3667315849216,
%T 1135407181398016,-441731548179726336,211079248633366839296,
%U -121507103129359646457856,82940335057202543199256576
%N E.g.f.: log(1+tanh(x)*tan(x))/2 (even powers only).
%e log(1+tanh(x)*tan(x))/2 = 1/2*x^2 - 1/4*x^4 + 11/45*x^6 - 73/360*x^8 +- ... .
%t Log[ 1+Tanh[ x ]*Tan[ x ]]/2 (* Even Part *)
%Y Cf. A009398.
%Y Cf. A101921.
%K sign
%O 0,3
%A _R. H. Hardin_
%E Extended with signs Mar 1997