A009758 - OEIS

%I #20 Feb 13 2018 02:54:13

%S 1,5,21,377,17161,442925,38819613,3394928609,307139569297,

%T 50204583973973,8330000263573413,1585633516380134729,

%U 416021432525199858841,118441213090527475221629,35638847609472720069131181,15336745055032862739772925873

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

%H G. C. Greubel, <a href="/A009758/b009758.txt">Table of n, a(n) for n = 1..242</a>

%t With[{nn=40},Take[CoefficientList[Series[Tan[x]/Cos[Tanh[x]],{x,0,nn}], x]*Range[0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Dec 08 2012 *)

%o (PARI) x='x+O('x^50); v=Vec(serlaplace(tan(x)/cos(tanh(x)))); vector((#v-1)\2 ,n,v[2*n-1]) \\ _G. C. Greubel_, Feb 12 2018

%K nonn

%O 1,2

%A _R. H. Hardin_

%E Extended and signs tested by _Olivier Gérard_, Mar 15 1997

%E More terms from _Harvey P. Dale_, Dec 08 2012