A211088 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors

1, 10, 240, 13872, 1924416, 641053824, 512493408768, 983311673066496, 4527565995515535360, 50027087182874567811072, 1326495212666507820379570176

Offset

1,2

Links

Table of n, a(n) for n=1..11.

Example

Some solutions for n=4
..3..1..3..1....2..1..0..3....1..2..3..2....1..1..3..0....2..1..0..3
..1..2..1..3....1..0..3..1....2..1..2..0....1..1..1..3....1..2..3..0
..3..1..0..1....0..3..1..2....3..2..1..3....3..1..1..2....0..3..0..1
..1..3..1..0....3..1..2..0....2..0..3..1....0..3..2..0....3..0..1..3

Crossrefs

Sequence in context: A221099 A171204 A156443 * A064757 A087435 A331611

Adjacent sequences: A211085 A211086 A211087 * A211089 A211090 A211091

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved