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A210927
Number of n X n 0..3 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
1
1, 5, 172, 38444, 36567600, 139088906848, 2108407726540016, 127364809805575916736, 30660305986899859448541568, 29412752846682454724638291977856
OFFSET
1,2
LINKS
EXAMPLE
Some solutions for n=4
..0..0..1..1....0..1..2..1....0..0..2..1....0..0..1..0....0..1..1..0
..0..0..2..2....1..1..2..1....0..1..3..3....0..1..2..2....1..0..0..1
..1..2..3..1....2..2..0..3....2..3..2..0....1..2..2..0....1..0..0..1
..1..2..1..0....1..1..3..3....1..3..0..0....0..2..0..2....0..1..1..0
CROSSREFS
Sequence in context: A206393 A220640 A198711 * A139986 A354573 A123111
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 29 2012
STATUS
approved