A211043 1/3 the number of n X n 0..2 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors.

0, 1, 8, 156, 7480, 898680, 266674964, 196750879896, 360466213243792, 1640421325318165822, 18541481770815952051304, 520535380394250894532873968, 36296751650483051319011293939152

Offset

1,3

Links

Table of n, a(n) for n=1..13.

Example

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

Crossrefs

Sequence in context: A251586 A221098 A171211 * A025605 A114223 A278669

Adjacent sequences: A211040 A211041 A211042 * A211044 A211045 A211046

Keyword

nonn

Author

R. H. Hardin, Mar 30 2012

Status

approved