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A211051 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors 0
1, 5, 45, 801, 27967, 1940165, 265677267, 71849269093, 38284388785363, 40154074645523977, 82859490626738386321, 336329579954192837096611, 2685093328682215861465741329 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
Some solutions for n=4
..0..1..0..0....0..1..0..1....2..0..2..0....2..2..2..2....2..1..2..2
..1..0..0..0....1..2..1..2....0..1..0..1....2..0..1..2....1..2..2..2
..0..0..2..1....0..1..2..0....2..0..1..0....2..1..2..2....2..2..2..2
..0..0..1..2....1..2..0..1....0..1..0..2....2..2..2..0....2..2..2..2
CROSSREFS
Sequence in context: A155104 A243951 A290941 * A322661 A191962 A326650
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 30 2012
STATUS
approved

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Last modified June 19 03:10 EDT 2024. Contains 373492 sequences. (Running on oeis4.)