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A202040
Number of zero-sum n X n -1..1 arrays with every element unequal to at most two horizontal and vertical neighbors
0
1, 19, 415, 31753, 6221993, 3573771563
OFFSET
1,2
COMMENTS
Diagonal of A202047
EXAMPLE
Some solutions for n=4
.-1.-1..0.-1...-1..1..1.-1....0..0..0..1...-1..0..0..1...-1.-1..0.-1
..1..0..0..0...-1.-1.-1.-1....1..0..0..1....0..0..0.-1....1..1..0..0
..1..0..0..0....1..1..1..1....1.-1.-1..1....1..1..0.-1....1..1..1..1
..0..1..1.-1....1..0..0.-1....0.-1.-1.-1....0..1..0.-1...-1.-1.-1..0
CROSSREFS
Sequence in context: A252927 A172740 A172816 * A244765 A069612 A077716
KEYWORD
nonn
AUTHOR
R. H. Hardin Dec 10 2011
STATUS
approved