Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #16 Feb 13 2018 03:13:07
%S 1,5,101,4297,311017,34201485,5316286925,1110355789329,
%T 300067100236625,101902284312853013,42484968788050104757,
%U 21335944225303831614809,12704193401200858575308601,8850034105543023432746843549,7130974518135579153768747620893
%N Expansion of e.g.f. tan(x)/cos(tan(x)), odd powers only.
%H G. C. Greubel, <a href="/A009757/b009757.txt">Table of n, a(n) for n = 0..224</a>
%t With[{nmax = 50}, CoefficientList[Series[Tan[x]/Cos[Tan[x]], {x, 0, nmax}], x]*Range[0, nmax - 1]!][[2 ;; ;; 2]] (* _G. C. Greubel_, Feb 12 2018 *)
%o (PARI) x='x+O('x^50); v=Vec(serlaplace(tan(x)/cos(tan(x)))); vector((#v-1)\2 ,n,v[2*n-1]) \\ _G. C. Greubel_, Feb 12 2018
%K nonn
%O 0,2
%A _R. H. Hardin_
%E Extended and signs tested by _Olivier Gérard_, Mar 15 1997