A211048 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors

1, 9, 226, 15556, 2941772, 1527584784, 2177623382864, 8522206940566808, 91558683282725300624, 2700384338082047133898512, 218639776300578162500042598232, 48597088081320286927152305357894272

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A330830 A218536 A338377 * A327146 A158728 A197406

Adjacent sequences: A211045 A211046 A211047 * A211049 A211050 A211051

Keyword

nonn

Author

R. H. Hardin Mar 30 2012

Status

approved