A193268 Number of n X n symmetric 0..2 arrays with no element equal to any horizontal or vertical neighbor and with new values 0..2 introduced in lower triangular row major order

1, 2, 12, 108, 1476, 30744, 978696, 47696148, 3562705944, 408229283700, 71800542715032, 19393574332167000, 8047409187443508720, 5131576344077602362144, 5029742282540253810124752

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..19

Example

Some solutions for 4X4
..0..1..0..1....0..1..2..0....0..1..0..2....0..1..0..1....0..1..2..0
..1..2..1..2....1..2..1..2....1..0..2..1....1..0..2..0....1..2..0..2
..0..1..2..0....2..1..2..1....0..2..0..2....0..2..0..1....2..0..2..1
..1..2..0..2....0..2..1..0....2..1..2..0....1..0..1..2....0..2..1..0

Crossrefs

Sequence in context: A194786 A339301 A179493 * A235601 A007724 A217800

Adjacent sequences: A193265 A193266 A193267 * A193269 A193270 A193271

Keyword

nonn

Author

R. H. Hardin Jul 20 2011

Status

approved