A211038 1/3 the number of n X n 0..2 symmetric matrices with every element equal to one or two horizontal and vertical neighbors

0, 1, 4, 72, 2088, 148758, 21763840, 7132571384, 5048293367644, 7844581606488974, 26582841246234004080, 197025807090354544802766

Offset

1,3

Links

Table of n, a(n) for n=1..12.

Example

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

Crossrefs

Sequence in context: A304316 A377356 A186415 * A203264 A295383 A309980

Adjacent sequences: A211035 A211036 A211037 * A211039 A211040 A211041

Keyword

nonn

Author

R. H. Hardin Mar 30 2012

Status

approved