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sec(sin(tanh(x))) = 1+1/2!*x^2-7/4!*x^4+73/6!*x^6+209/8!*x^8...
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%I #14 Oct 27 2023 21:05:57

%S 1,1,-7,73,209,-144271,16935049,-1681509255,121927140641,

%T 7429711841377,-7368737635468135,2672443484700215337,

%U -714451608564077085455,102412390388191040345041,45342663705298790615837737,-56227306534265498361644426407

%N sec(sin(tanh(x))) = 1+1/2!*x^2-7/4!*x^4+73/6!*x^6+209/8!*x^8...

%H Alois P. Heinz, <a href="/A012049/b012049.txt">Table of n, a(n) for n = 0..100</a> (terms n = 0..50 from Vincenzo Librandi)

%t With[{nn=40},Take[CoefficientList[Series[Sec[Sin[Tanh[x]]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Sep 25 2013 *)

%K sign

%O 0,3

%A Patrick Demichel (patrick.demichel(AT)hp.com)

%E More terms from _Harvey P. Dale_, Sep 25 2013