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Expansion of e.g.f. tan(tan(x))/cos(x), odd powers only.
1

%I #25 Apr 20 2014 09:25:13

%S 1,7,137,5535,386481,41604055,6390472441,1326107352879,

%T 357130810766305,121056393177867303,50420813008501457897,

%U 25307979564532627724095,15065045963101006722139793

%N Expansion of e.g.f. tan(tan(x))/cos(x), odd powers only.

%H Vincenzo Librandi, <a href="/A009701/b009701.txt">Table of n, a(n) for n = 0..100</a>

%F a(n) ~ 4 * (2*n+1)! / (sqrt(4+Pi^2) * (arctan(Pi/2))^(2*n+2)). - _Vaclav Kotesovec_, Apr 20 2014

%t With[{nn=30},Take[CoefficientList[Series[Tan[Tan[x]]/Cos[x],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Aug 25 2013 *)

%K nonn

%O 0,2

%A _R. H. Hardin_

%E Extended and signs tested by _Olivier GĂ©rard_, Mar 15 1997

%E Prior Mathematica program deleted by _Harvey P. Dale_, Aug 25 2013

%E Clarified definition - _Joerg Arndt_, Feb 09 2014