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%I #16 Oct 26 2023 08:26:16
%S 1,3,280,6028059
%N Number of nonisomorphic acyclic orientations of the Hamming graph (K_n) x (K_n).
%C Also number of plans (i.e., structural solutions) of the open shop problem with n jobs and n machines where the jobs may be interchanged with the machines - see problems in scheduling theory.
%D Martin Harborth, Structural analysis of shop scheduling problems, PhD thesis, Otto-von-Guericke-Univ. Magdeburg, GCA-Verlag, 1999. (in German)
%H H. Bräsel, M. Harborth, T. Tautenhahn and P. Willenius, <a href="https://doi.org/10.1023/A:1018938915709">On the set of solutions of the open shop problem</a>, Ann. Oper. Res. 92 (1999) 241-263.
%Y Cf. A053870.
%K nonn,nice,hard,more
%O 1,2
%A Martin Harborth (Martin.Harborth(AT)vt.siemens.de)