A208866 Number of n X 2 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.

2, 12, 143, 1979, 28246, 405481, 5826959, 83752328, 1203835147, 17303737555, 248721498050, 3575088704597, 51387836750983, 738641752044964, 10617135747615911, 152609260439813291, 2193584684852893774

Offset

1,1

Comments

Column 2 of A208872.

Links

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

Formula

Empirical: a(n) = 18*a(n-1) - 55*a(n-2) + 42*a(n-3) - 9*a(n-4) for n>5.

Empirical g.f.: x*(2 - 24*x + 37*x^2 - 19*x^3 + 3*x^4) / ((1 - 3*x + x^2)*(1 - 15*x + 9*x^2)). - Colin Barker, Jul 07 2018

Example

Some solutions for n=4:
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..1....0..0
..1..0....1..0....1..0....1..1....1..0....1..0....1..1....1..2....1..2....1..1
..1..2....1..0....1..1....0..0....0..2....0..1....2..1....3..3....0..1....2..0
..3..2....2..2....2..0....1..0....1..3....1..2....0..3....0..1....0..0....1..1

Crossrefs

Cf. A208872.

Sequence in context: A240387 A087800 A009747 * A334174 A067601 A365284

Adjacent sequences: A208863 A208864 A208865 * A208867 A208868 A208869

Keyword

nonn

Author

R. H. Hardin, Mar 02 2012

Status

approved