A186481 Number of (n+1)X9 0..3 arrays with every 2X2 subblock commuting with each of its horizontal and vertical 2X2 subblock neighbors

27101, 35081, 101108, 286290, 479785, 1286113, 1894849, 5977657, 8078233, 25049545, 34600393, 103930809, 154520201, 437740901, 693356465, 1854858401, 3085313121, 7883094433, 13654582357, 33612555865, 60183013369, 143706271561

Offset

1,1

Comments

Column 8 of A186482

Links

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

Formula

Empirical: a(n)=2*a(n-1)+2*a(n-2)-6*a(n-3)+6*a(n-4)-3*a(n-5) for n>19

Example

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

Crossrefs

Sequence in context: A236825 A164522 A037045 * A210073 A236275 A228562

Adjacent sequences: A186478 A186479 A186480 * A186482 A186483 A186484

Keyword

nonn

Author

R. H. Hardin Feb 22 2011

Status

approved