A186873 Number of (n+2)X3 0..3 arrays with every 3X3 subblock commuting with each horizontal and vertical neighbor 3X3 subblock

262144, 2428, 19236, 46583, 104701, 186096, 277659, 322910, 569446, 975469, 1428461, 2729288, 4782807, 7112898, 12726103, 21815463, 33093523, 58123410, 99742321, 154917607, 268187989, 458493523, 723302362, 1237486150, 2107632127

Offset

1,1

Comments

Column 1 of A186881

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n)=2*a(n-1)-a(n-2)+3*a(n-3)-6*a(n-4)+3*a(n-5)+3*a(n-6)-3*a(n-7) for n>20

Example

Some solutions for 4X3
..3..3..0....1..0..1....0..3..0....2..0..0....0..0..0....2..0..0....0..0..0
..0..3..3....2..0..0....0..0..0....0..0..2....0..0..0....0..2..0....0..0..0
..0..3..0....0..2..0....0..0..0....0..0..2....1..1..0....0..0..2....2..3..0
..0..0..3....0..0..2....0..2..2....0..0..2....2..3..1....2..1..3....0..0..3

Crossrefs

Sequence in context: A069393 A186872 A186881 * A018867 A057445 A069279

Adjacent sequences: A186870 A186871 A186872 * A186874 A186875 A186876

Keyword

nonn

Author

R. H. Hardin Feb 28 2011

Status

approved