A186471 Number of (n+1)X9 0..2 arrays with every 2X2 subblock commuting with each of its horizontal and vertical 2X2 subblock neighbors

4553, 5790, 13985, 31866, 52755, 109950, 170811, 399018, 570183, 1266414, 1812423, 3993474, 6107001, 13004678, 20863681, 42650908, 70588930, 140178754, 237788174, 462275652, 798678366, 1528016844, 2676404634, 5059638908, 8953777234

Offset

1,1

Comments

Column 8 of A186472

Links

R. H. Hardin, Table of n, a(n) for n = 1..78

Formula

Empirical: a(n)=2*a(n-1)+a(n-2)-4*a(n-3)+4*a(n-4)-2*a(n-5) for n>17

Example

Some solutions for 3X9
..1..0..1..0..0..0..0..1..2....0..0..0..2..0..0..0..0..0
..0..1..0..1..0..0..0..0..1....1..0..0..0..2..0..0..0..0
..0..0..1..0..1..0..0..0..0....0..1..0..0..0..2..0..0..0

Crossrefs

Sequence in context: A031607 A193311 A020432 * A210305 A102748 A032751

Adjacent sequences: A186468 A186469 A186470 * A186472 A186473 A186474

Keyword

nonn

Author

R. H. Hardin Feb 22 2011

Status

approved