A183713 1/20 of the number of (n+1) X 4 0..4 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease.

12, 54, 224, 950, 4012, 16964, 71712, 303170, 1281664, 5418314, 22906232, 96837444, 409385940, 1730703022, 7316648160, 30931557950, 130764969444, 552816553732, 2337064300200, 9880075964922, 41768598769664, 176579193270290

Offset

1,1

Comments

Column 3 of A183719.

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + 10*a(n-2) - 10*a(n-4) - 2*a(n-5) + a(n-6).

Empirical g.f.: 2*x*(6 + 15*x - 2*x^2 - 19*x^3 - 4*x^4 + 2*x^5) / ((1 - x)*(1 + x)*(1 - 2*x - 9*x^2 - 2*x^3 + x^4)). - Colin Barker, Apr 04 2018

Example

Some solutions for 3 X 4:
..0..4..1..4....0..4..0..4....4..0..4..0....3..0..3..4....3..2..3..2
..2..3..2..3....1..2..1..3....3..2..3..2....2..1..2..0....0..1..0..1
..0..4..1..0....0..3..0..4....0..1..4..0....3..4..3..4....3..2..4..2
...
...L..R..L.......L..R..L.......R..L..R.......R..L..R.......L..R..L...
...R..L..R.......R..L..R.......L..R..L.......L..R..L.......R..L..R...

Crossrefs

Cf. A183719.

Sequence in context: A025204 A005549 A124858 * A126399 A137938 A009726

Adjacent sequences: A183710 A183711 A183712 * A183714 A183715 A183716

Keyword

nonn

Author

R. H. Hardin, Jan 06 2011

Status

approved