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%I #9 May 17 2020 01:41:03
%S 1,1,3,19,391,25532,5536654,4102276124,10576325574496,
%T 96132191056438654,3112190512707436846248,361888107612909923618319047,
%U 152218183506656720143679173709254,233008581159686014846657554273887832751
%N Number of lower triangles of an n X n 0..5 array with all row sums equal to the length of the row and all column sums equal to the length of the column.
%e Some solutions for n=5:
%e ..1..........1..........1..........1..........1..........1..........1
%e ..0.2........1.1........0.2........0.2........2.0........1.1........0.2
%e ..0.1.2......0.1.2......0.2.1......2.1.0......2.1.0......0.1.2......1.0.2
%e ..3.1.0.0....2.1.1.0....4.0.0.0....1.0.2.1....0.3.1.0....2.2.0.0....2.1.0.1
%e ..1.0.1.2.1..1.1.0.2.1..0.0.2.2.1..1.1.1.1.1..0.0.2.2.1..1.0.1.2.1..1.1.1.1.1
%Y Column 5 of A195644.
%K nonn
%O 1,3
%A _R. H. Hardin_, Sep 21 2011
%E a(12)-a(14) from _Andrew Howroyd_, May 16 2020
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