A183730 1/16 the number of (n+1) X 2 0..7 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease, and at least two adjacent blocks having the same increasing direction.

0, 21, 563, 9403, 135578, 1814815, 23204876, 287769879, 3491293862, 41667398364, 490998416023, 5727556631915, 66266101711488, 761498455531330, 8701271226331052, 98948856313647335, 1120614615517688964

Offset

1,2

Comments

Column 1 of A183738.

Links

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

Formula

Empirical: a(n)=18*a(n-1)-46*a(n-2)-342*a(n-3)-33*a(n-4)+435*a(n-5)-157*a(n-6)-37*a(n-7)+21*a(n-8)-2*a(n-9).

Example

Some solutions with the first block increasing clockwise for 3 X 2:
..4..5....6..0....1..2....1..2....2..4....4..5....7..0....2..3....0..2....0..2
..2..6....5..1....7..4....0..3....0..5....1..6....6..1....1..4....7..3....6..3
..1..7....4..2....6..5....7..4....7..6....0..7....4..3....0..7....6..4....5..4
...
...R.......R.......R.......R.......R.......R.......R.......R.......R.......R...
...R.......R.......R.......R.......R.......R.......R.......R.......R.......R...

Crossrefs

Sequence in context: A297635 A292062 A194022 * A341572 A199254 A199199

Adjacent sequences: A183727 A183728 A183729 * A183731 A183732 A183733

Keyword

nonn

Author

R. H. Hardin, Jan 06 2011

Status

approved