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A193785
Number of n X n symmetric 0..6 arrays with no element equal to the sum or difference mod 7 of any two of its horizontal and vertical neighbors
0
7, 120, 2424, 139320, 19924728, 7436532066, 7374601234200, 19007056742693388, 127460953360341764580, 2242822081859232960548754
OFFSET
1,1
EXAMPLE
Some solutions for 4X4
..5..2..1..2....3..1..6..4....1..1..3..1....4..4..4..3....3..4..4..4
..2..2..2..2....1..6..6..1....1..1..3..1....4..4..3..3....4..3..3..2
..1..2..2..5....6..6..6..1....3..3..1..6....4..3..3..2....4..3..4..3
..2..2..5..6....4..1..1..3....1..1..6..3....3..3..2..3....4..2..3..2
CROSSREFS
Sequence in context: A263943 A302718 A007751 * A253276 A156955 A196796
KEYWORD
nonn
AUTHOR
R. H. Hardin Aug 05 2011
STATUS
approved