A211051 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors

1, 5, 45, 801, 27967, 1940165, 265677267, 71849269093, 38284388785363, 40154074645523977, 82859490626738386321, 336329579954192837096611, 2685093328682215861465741329

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A155104 A243951 A290941 * A322661 A191962 A326650

Adjacent sequences: A211048 A211049 A211050 * A211052 A211053 A211054

Keyword

nonn

Author

R. H. Hardin Mar 30 2012

Status

approved