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%I #17 Apr 16 2017 04:52:31
%S 0,56,419250816,2294248126968596791296,
%T 71871209790288983974921874964480000000000,
%U 70222282105561329499166350697268240329817049897201827840000000000000
%N Number of disjoint non-ordered pairs of n^2 X n^2 S-permutation matrices.
%C Note that although the two Yordzhev papers have similar titles, they are different papers.
%H Krasimir Yordzhev, <a href="https://arxiv.org/abs/1211.1628">On the Number of Disjoint Pairs of S-permutation Matrices</a>, arXiv:12112:1628 [math.CO], 2012.
%H Krasimir Yordzhev, <a href="http://doi.org/10.1016/j.disc.2016.09.011">On the number of mutually disjoint pairs of S-permutation matrices</a>, Discrete Mathematics 340 (2017) 1442-1448.
%F a(n) = A285178(n)*(n!)^(2*n)/2.
%Y Cf. A107739, A285178, A285180.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Apr 14 2017
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