%I A012393
%S A012393 2,16,512,34816,4063232,724566016,183240753152,62382319599616,
%T A012393 27507470234550272,15250953398036463616,10384044045105304174592,
%U A012393 8517992937742473694806016,8285310016381680852100186112
%N A012393 arctanh(tan(x)*tan(x))=2/2!*x^2+16/4!*x^4+512/6!*x^6+34816/8!*x^8...
%F A012393 E.g.f.: ln(sec(2*x))/2, cf. A000182. - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Jun 04 2005
%Y A012393 Sequence in context: A140311 A012389 A009710 this_sequence A063387 A063391 
               A002416
%Y A012393 Adjacent sequences: A012390 A012391 A012392 this_sequence A012394 A012395 
               A012396
%K A012393 nonn
%O A012393 0,1
%A A012393 Patrick Demichel (dml(AT)hpfrcu03.france.hp.com)