A202982 Number of n X 2 0..2 arrays with every nonzero element less than or equal to some NW, E or S neighbor.

1, 9, 63, 323, 1629, 8534, 44885, 234728, 1226239, 6410598, 33519355, 175245104, 916179060, 4789827101, 25041566175, 130918895222, 684451568104, 3578352893257, 18707840821315, 97805696796991, 511333945789384

Offset

1,2

Comments

Column 2 of A202988.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 9*a(n-1) -28*a(n-2) +60*a(n-3) -102*a(n-4) +84*a(n-5) -44*a(n-6) +25*a(n-7).

Empirical g.f.: x*(1 + 10*x^2 - 52*x^3 + 48*x^4 - 29*x^5 + 25*x^6) / (1 - 9*x + 28*x^2 - 60*x^3 + 102*x^4 - 84*x^5 + 44*x^6 - 25*x^7). - Colin Barker, Jun 03 2018

Example

Some solutions for n=5:
..1..1....1..0....2..0....0..0....2..0....1..0....0..1....0..1....0..1....1..0
..1..1....1..1....2..0....0..2....2..2....2..1....2..1....2..2....2..1....1..2
..1..1....0..0....2..0....2..2....1..1....2..1....2..2....1..2....2..2....2..2
..2..0....1..1....2..2....2..2....2..1....2..0....1..1....1..1....2..1....0..2
..2..2....0..1....1..1....1..1....2..2....2..2....0..0....1..1....2..2....0..0

Crossrefs

Cf. A202988.

Sequence in context: A379683 A178161 A015669 * A073378 A316461 A022733

Adjacent sequences: A202979 A202980 A202981 * A202983 A202984 A202985

Keyword

nonn

Author

R. H. Hardin, Dec 26 2011

Status

approved