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A210900
Number of n X n 0..2 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order
1
1, 5, 102, 6390, 1086041, 502575673, 633196217205, 2172041686544831, 20286478141700961127, 515885869356108286483984, 35719903989356689494965133243, 6734055759629373955660905711394302
OFFSET
1,2
LINKS
EXAMPLE
Some solutions for n=4
..0..1..0..1....0..1..2..2....0..0..1..1....0..1..1..2....0..0..1..1
..1..0..1..1....1..1..0..1....0..1..2..0....1..1..0..0....0..1..0..0
..0..1..1..2....2..0..2..0....1..2..1..2....1..0..1..0....1..0..2..2
..1..1..2..2....2..1..0..1....1..0..2..2....2..0..0..1....1..0..2..0
CROSSREFS
Sequence in context: A231830 A260024 A123626 * A197799 A266903 A052138
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 29 2012
STATUS
approved