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%I #10 Oct 11 2014 02:13:50
%S 1,2,22,2418,4276864
%N Number of lower triangular n X n arrays of integers 0 upwards introduced in row major order, with each element unique in its row and column.
%e Some solutions for n=4:
%e ..0........0........0........0........0........0........0........0
%e ..1.2......1.2......1.0......1.2......1.2......1.2......1.2......1.0
%e ..3.4.1....3.4.5....2.3.4....3.0.4....3.4.5....3.1.4....3.4.5....2.3.4
%e ..5.3.4.2..5.1.4.3..5.2.0.1..4.5.3.6..5.6.4.2..2.5.3.4..6.5.7.0..5.6.3.2
%K nonn,more
%O 1,2
%A _R. H. Hardin_, Apr 24 2012
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