A210908 Number of n X n 0..2 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order.

1, 5, 113, 7778, 1470886, 763792392, 1088811691432, 4261103470283404, 45779341641362650312, 1350192169041023566949256, 109319888150289081250021299116, 24298544040660143463576152678947136

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..13

Example

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

Crossrefs

Sequence in context: A009678 A009691 A194570 * A355074 A053712 A325914

Adjacent sequences: A210905 A210906 A210907 * A210909 A210910 A210911

Keyword

nonn

Author

R. H. Hardin, Mar 29 2012

Status

approved