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%I A012748 #15 Jun 21 2024 14:35:07
%S A012748 1,1,1,25,3617,340145,40490657,7034559753,1668333374913,
%T A012748 504856533178465,189500285350524865,86696156445549770233,
%U A012748 47524548345395009982689,30739504895562596416971025,23162222253680333719652996449,20112913566033287819336502367465,19939158697176271310635403636418945
%N A012748 Expansion of e.g.f. sec(arctanh(x)*cos(x)), only even powers.
%H A012748 Stefano Spezia, <a href="/A012748/b012748.txt">Table of n, a(n) for n = 0..150</a>
%e A012748 E.g.f. = 1 + x^2/2! + x^4/4! + 25*x^6/6! + 3617*x^8/8! + ...
%t A012748 nmax=32; DeleteCases[CoefficientList[Series[Sec[ArcTanh[x]Cos[x]],{x,0,nmax}],x],0](2Range[0,nmax/2])!  (* _Stefano Spezia_, Jun 21 2024 *)
%K A012748 nonn
%O A012748 0,4
%A A012748 Patrick Demichel (patrick.demichel(AT)hp.com)
%E A012748 a(14)-a(16) from _Stefano Spezia_, Jun 21 2024

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