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A210906 Number of n X n 0..2 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 0
1, 3, 20, 258, 5316, 175508, 9246604, 778330944, 104490906936, 22379344947816, 7640730937406288, 4158457819686881368, 3606450263851909019488 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
Some solutions for n=4
..0..1..0..1....0..1..0..1....0..1..0..1....0..1..1..2....0..1..0..1
..1..2..1..0....1..0..1..2....1..2..1..0....1..1..1..0....1..0..2..2
..0..1..0..2....0..1..2..1....0..1..2..1....1..1..2..2....0..2..2..2
..1..0..2..0....1..2..1..0....1..0..1..2....2..0..2..2....1..2..2..1
CROSSREFS
Sequence in context: A331504 A197322 A197975 * A355215 A193194 A320945
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 29 2012
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)