A211044 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors

1, 9, 216, 15444, 3281472, 2067554808, 3863711228544, 21415460458704264, 352065294244909032696, 17166897737612437082259600, 2482751631736501357900013730432, 1064995044786220639044258688726569096

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..16

Example

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

Crossrefs

Sequence in context: A084942 A061718 A085741 * A152288 A179153 A197669

Adjacent sequences: A211041 A211042 A211043 * A211045 A211046 A211047

Keyword

nonn

Author

R. H. Hardin Mar 30 2012

Status

approved