A211089 1/4 the number of n X n 0..3 symmetric matrices with every element equal to one or two horizontal and vertical neighbors

0, 1, 6, 348, 28140, 8126604, 5661794106, 11445238420311, 62094025253816664, 936614735379619968930, 38691771579576015771775929

Offset

1,3

Links

Table of n, a(n) for n=1..11.

Example

Some solutions for n=4
..2..2..0..3....0..0..3..3....1..1..0..0....2..2..2..3....0..0..0..0
..2..0..0..3....0..0..0..3....1..2..2..3....2..3..3..3....0..1..1..2
..0..0..1..1....3..0..0..0....0..2..2..3....2..3..1..1....0..1..1..2
..3..3..1..1....3..3..0..0....0..3..3..3....3..3..1..1....0..2..2..2

Crossrefs

Sequence in context: A047941 A229501 A289738 * A221923 A000409 A214445

Adjacent sequences: A211086 A211087 A211088 * A211090 A211091 A211092

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved