A210906 Number of n X n 0..2 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order

1, 3, 20, 258, 5316, 175508, 9246604, 778330944, 104490906936, 22379344947816, 7640730937406288, 4158457819686881368, 3606450263851909019488

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A331504 A197322 A197975 * A355215 A193194 A320945

Adjacent sequences: A210903 A210904 A210905 * A210907 A210908 A210909

Keyword

nonn

Author

R. H. Hardin Mar 29 2012

Status

approved