A211087 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors

1, 9, 324, 35343, 12487068, 14118092100, 51199696832895, 595365272306224965, 22199455509688700548632, 2654252181204304007637930258, 1017614219466672806577892453493568

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A156634 A128788 A164080 * A211091 A124070 A203763

Adjacent sequences: A211084 A211085 A211086 * A211088 A211089 A211090

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved