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A210907
Number of n X n 0..2 symmetric matrices with every element equal to one or two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order
0
0, 1, 2, 51, 1726, 153098, 28152650, 11567939904, 10468180657260, 20883980738963652, 92033224229940826385, 894504588855167462245204
OFFSET
1,3
EXAMPLE
Some solutions for n=4
..0..0..1..1....0..0..0..0....0..0..0..0....0..0..2..2....0..0..1..2
..0..0..2..0....0..1..1..0....0..1..1..0....0..1..1..2....0..0..1..2
..1..2..2..0....0..1..1..0....0..1..2..2....2..1..1..1....1..1..1..0
..1..0..0..0....0..0..0..0....0..0..2..2....2..2..1..1....2..2..0..0
CROSSREFS
Sequence in context: A106042 A222850 A089304 * A099368 A132492 A030264
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 29 2012
STATUS
approved