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A165380
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
0
1, 40, 1012, 18900, 598332, 30346872, 3445935988
OFFSET
2,2
EXAMPLE
Some solutions for n=4
...1.1.1.2.........1.2.2.2.........1.1.1.2.........1.1.4.2......
.....2.2.2.4.........2.2.2.2.........1.1.2.2.........4.4.2.4....
.......2.3.4.4.........3.3.2.4.........1.1.2.4.........4.4.4.4..
.........3.4.4.4.........3.3.4.4.........3.2.4.4.........3.3.4.4
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...1.2.2.2.........1.2.2.2.........1.1.2.2.........1.1.1.2......
.....3.3.2.2.........3.3.2.4.........2.2.2.2.........2.2.2.2....
.......3.3.2.2.........3.3.4.4.........3.3.2.2.........3.3.3.4..
.........3.2.2.4.........3.3.4.4.........3.3.4.4.........3.3.4.4
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...1.1.1.2.........1.1.2.2.........1.1.1.2.........1.1.2.2......
.....1.1.2.2.........1.1.3.3.........2.2.2.2.........1.2.2.2....
.......3.3.3.4.........1.3.3.4.........3.3.2.3.........3.3.2.4..
.........3.4.4.4.........3.3.4.4.........3.3.3.4.........3.3.4.4
CROSSREFS
Sequence in context: A004349 A016092 A028228 * A075907 A062143 A284838
KEYWORD
nonn
AUTHOR
R. H. Hardin Sep 17 2009
STATUS
approved