A210910 Number of n X n 0..2 symmetric matrices with every element equal to zero, two, three or four horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order.

1, 3, 23, 401, 13984, 970083, 132838634, 35924634547, 19142194392682, 20077037322761989, 41429745313369193161, 168164789977096418548306

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A233218 A114601 A178315 * A280654 A118195 A055326

Adjacent sequences: A210907 A210908 A210909 * A210911 A210912 A210913

Keyword

nonn,more

Author

R. H. Hardin, Mar 29 2012

Extensions

Name corrected by Andrew Howroyd, Mar 25 2025

Status

approved