A186469 Number of (n+1) X 7 0..2 arrays with every 2 X 2 subblock commuting with each of its horizontal and vertical 2 X 2 subblock neighbors.

1321, 1754, 4023, 9834, 16083, 34314, 49407, 109950, 159879, 350418, 540777, 1143302, 1845649, 3753244, 6241282, 12344866, 21014030, 40729476, 70552158, 134674572, 236349786, 446055356, 790511890, 1479273964, 2640888394

Offset

1,1

Comments

Column 6 of A186472.

Links

R. H. Hardin, Table of n, a(n) for n = 1..170

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>15.

Example

Some solutions for 3 X 7
..2..0..0..0..2..0..1....2..2..0..0..0..0..1....2..1..0..0..0..1..0
..2..0..0..0..0..2..0....1..0..2..0..0..0..1....1..0..1..0..0..0..1
..2..0..0..0..0..0..2....0..1..0..2..0..0..1....0..1..0..1..0..0..2

Crossrefs

Cf. A186472.

Sequence in context: A092088 A068302 A139666 * A145754 A020403 A249080

Adjacent sequences: A186466 A186467 A186468 * A186470 A186471 A186472

Keyword

nonn

Author

R. H. Hardin, Feb 22 2011

Status

approved