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%I #11 Feb 25 2018 20:36:54
%S 1,1,1,3,9,45,225,1071,6993,56697,467745,3279419,29529753,376156261,
%T 4297350785,35274762407,378759492257,8003761282417,122599030798017,
%U 853554115621363,8002975063348265,450081179390735645
%N Expansion of e.g.f. exp(sec(x)*arcsinh(x)).
%C The first negative number is a(24) = -686072407102337430543.
%H Andrew Howroyd, <a href="/A012821/b012821.txt">Table of n, a(n) for n = 0..200</a>
%e exp(sec(x)*arcsinh(x)) = 1 + x + 1/2!*x^2 + 3/3!*x^3 + 9/4!*x^4 + 45/5!*x^5 + ...
%o (PARI) seq(n)={my(x='x+O('x^n)); Vec(serlaplace(exp(asinh(x)/cos(x))))} \\ _Andrew Howroyd_, Feb 25 2018
%K sign
%O 0,4
%A Patrick Demichel (patrick.demichel(AT)hp.com)
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