A211041 1/3 the number of n X n 0..2 symmetric matrices with every element equal to two or three horizontal and vertical neighbors.

0, 1, 0, 6, 8, 118, 880, 14400, 318220, 10446298, 531060152, 39577654480, 4465022457276, 757302604610482, 191605833481050984

Offset

1,4

Links

Table of n, a(n) for n=1..15.

Example

Some solutions for n=4
..0..0..1..1....0..0..1..1....2..2..0..0....2..2..1..1....1..1..1..1
..0..0..1..1....0..0..1..1....2..2..0..0....2..2..1..1....1..2..2..1
..1..1..0..0....1..1..2..2....0..0..1..1....1..1..2..2....1..2..2..1
..1..1..0..0....1..1..2..2....0..0..1..1....1..1..2..2....1..1..1..1

Crossrefs

Sequence in context: A013234 A013240 A161801 * A236754 A069660 A119001

Adjacent sequences: A211038 A211039 A211040 * A211042 A211043 A211044

Keyword

nonn

Author

R. H. Hardin, Mar 30 2012

Status

approved