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%I #4 Dec 18 2015 18:17:24
%S 1,40,1012,18900,598332,30346872,3445935988
%N Number of slanted n X n (i=1..n)X(j=i..n+i-1) 1..4 arrays with all 1s connected, all 2s connected, all 3s connected, all 4s connected, 1 in the upper left corner, 2 in the upper right corner, 3 in the lower left corner, 4 in the lower right corner, and with no element having more than 3 neighbors with the same value
%e Some solutions for n=4
%e ...1.1.1.2.........1.2.2.2.........1.1.1.2.........1.1.4.2......
%e .....2.2.2.4.........2.2.2.2.........1.1.2.2.........4.4.2.4....
%e .......2.3.4.4.........3.3.2.4.........1.1.2.4.........4.4.4.4..
%e .........3.4.4.4.........3.3.4.4.........3.2.4.4.........3.3.4.4
%e ------
%e ...1.2.2.2.........1.2.2.2.........1.1.2.2.........1.1.1.2......
%e .....3.3.2.2.........3.3.2.4.........2.2.2.2.........2.2.2.2....
%e .......3.3.2.2.........3.3.4.4.........3.3.2.2.........3.3.3.4..
%e .........3.2.2.4.........3.3.4.4.........3.3.4.4.........3.3.4.4
%e ------
%e ...1.1.1.2.........1.1.2.2.........1.1.1.2.........1.1.2.2......
%e .....1.1.2.2.........1.1.3.3.........2.2.2.2.........1.2.2.2....
%e .......3.3.3.4.........1.3.3.4.........3.3.2.3.........3.3.2.4..
%e .........3.4.4.4.........3.3.4.4.........3.3.3.4.........3.3.4.4
%K nonn
%O 2,2
%A _R. H. Hardin_ Sep 17 2009
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