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%I #3 Aug 09 2019 14:29:30
%S 0,0,1,0,-10,0,183,0,-5540,0,252605,0,-16216590,0,1395526867,0,
%T -155132097160,0,21643917078969,0,-3703711882375250,0,
%U 762837618324516911,0,-186174409962685042860,0,53131942620810610600693,0,-17531634979650818116555990,0
%N a(n) = n! * [x^n] (x * tanh(x) * sech(x)) / 2.
%F E.g.f.: x*(exp(x) - exp(-x))/(exp(x) + exp(-x))^2.
%p egf := x*tanh(x)*sech(x)/2: ser := series(egf, x, 30):
%p seq(n!*coeff(ser, x, n), n=0..29);
%Y a(n) = A326722(n, 3) for n >= 0.
%K sign
%O 0,5
%A _Peter Luschny_, Aug 09 2019
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