A210909 Number of n X n 0..2 symmetric matrices with every element equal to zero, one, three or four horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order.

1, 2, 24, 616, 34972, 4448872, 1271872472, 816403740024, 1175380974129748, 3797950184579806600, 27543816778839681854992, 448288796291335397449297608

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A128578 A186632 A089835 * A009251 A009447 A193442

Adjacent sequences: A210906 A210907 A210908 * A210910 A210911 A210912

Keyword

nonn,more

Author

R. H. Hardin, Mar 29 2012

Extensions

Name corrected by Andrew Howroyd, Mar 25 2025

Status

approved