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%I #14 Sep 08 2022 08:45:07
%S 1,1,3,15,96,720,6120,57960,604800,6894720,85276800,1137628800,
%T 16286054400,249080832000,4053790540800,69960578688000,
%U 1276290183168000,24542432538624000,496183962193920000,10522301185363968000
%N Related to number of labeled partially ordered sets.
%H G. C. Greubel, <a href="/A076301/b076301.txt">Table of n, a(n) for n = 0..445</a>
%H M. Janjic and B. Petkovic, <a href="http://arxiv.org/abs/1301.4550">A Counting Function</a>, arXiv 1301.4550 [math.CO], 2013
%F E.g.f.: -(2-4*x + 3*x^2)/(-6*x^2 - 2 + 6*x + 2*x^3).
%F a(n) = (4 - n + n^2)*n!/4. - _G. C. Greubel_, May 04 2018
%p seq(1/4*(4-n+n^2)*n!,n=0..30);
%t Table[(4 -n +n^2)*n!/4, {n,0,30}] (* _G. C. Greubel_, May 04 2018 *)
%o (PARI) for(n=0, 30, print1((4 -n +n^2)*n!/4, ", ")) \\ _G. C. Greubel_, May 04 2018
%o (Magma) [(4 -n +n^2)*Factorial(n)/4: n in [0..30]]; // _G. C. Greubel_, May 04 2018
%K nonn
%O 0,3
%A Detlef Pauly (dettodet(AT)yahoo.de), Mar 14 2003
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