login
A210921
Number of n X n 0..3 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order.
0
1, 3, 39, 2107, 277902, 87883641, 66460660741, 120226326939778, 520179215730042235, 5383068220104980704743, 133236771262960489496028245
OFFSET
1,2
EXAMPLE
Some solutions for n=4
..0..1..0..3....0..0..1..1....0..1..1..1....0..1..0..1....0..1..2..3
..1..2..1..2....0..0..1..1....1..1..0..1....1..0..1..2....1..0..3..1
..0..1..2..3....1..1..2..0....1..0..1..1....0..1..2..0....2..3..0..0
..3..2..3..1....1..1..0..1....1..1..1..2....1..2..0..2....3..1..0..0
CROSSREFS
Sequence in context: A084881 A193122 A015017 * A290516 A210925 A300046
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 29 2012
STATUS
approved