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A210929
Number of n X n 0..3 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
0
1, 3, 42, 2316, 320744, 106842320, 85415568160, 163885278844480, 754594332585922688, 8337847863812427968768, 221082535444417970063262208
OFFSET
1,2
EXAMPLE
Some solutions for n=4
..0..0..1..3....0..1..0..1....0..1..0..2....0..1..2..3....0..1..3..0
..0..0..2..1....1..2..3..2....1..0..2..3....1..0..3..2....1..2..0..2
..1..2..0..2....0..3..0..0....0..2..0..2....2..3..2..3....3..0..2..1
..3..1..2..1....1..2..0..0....2..3..2..3....3..2..3..0....0..2..1..3
CROSSREFS
Sequence in context: A333323 A331705 A156108 * A083402 A145984 A213956
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 29 2012
STATUS
approved