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A210925
Number of n X n 0..3 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
0
1, 3, 39, 2212, 314852, 110451021, 95121973827, 200885189935045, 1039262747697700932, 13162671799070468638683
OFFSET
1,2
EXAMPLE
Some solutions for n=4
..0..1..2..3....0..1..2..3....0..1..0..1....0..1..0..3....0..1..2..1
..1..0..1..2....1..0..1..0....1..2..1..3....1..0..2..1....1..2..3..0
..2..1..3..3....2..1..0..2....0..1..2..1....0..2..1..3....2..3..2..3
..3..2..3..3....3..0..2..1....1..3..1..2....3..1..3..0....1..0..3..1
CROSSREFS
Sequence in context: A015017 A210921 A290516 * A300046 A267624 A342178
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 29 2012
STATUS
approved