A211091 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors

1, 9, 324, 36801, 13804290, 17121995676, 70150653652257, 949536762106019733, 42462806002512959389608, 6273638029264294190600689986

Offset

1,2

Links

Table of n, a(n) for n=1..10.

Example

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

Crossrefs

Sequence in context: A128788 A164080 A211087 * A124070 A203763 A041619

Adjacent sequences: A211088 A211089 A211090 * A211092 A211093 A211094

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved