A230835 Number of n X 2 0..3 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value (x(i,j)+1) mod 4, and upper left element zero.

0, 2, 22, 162, 1202, 8974, 66990, 500018, 3732178, 27857358, 207930158, 1552011826, 11584373970, 86466944462, 645398059822, 4817316700722, 35956941366482, 268386264128974, 2003262347565870, 14952553724011058, 111607380401824978

Offset

1,2

Links

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

Formula

Empirical: a(n) = 8*a(n-1) - 5*a(n-2) + 8*a(n-3) - 4*a(n-4).

Empirical g.f.: 2*x^2*(1 + 3*x - 2*x^2) / ((1 + x^2)*(1 - 8*x + 4*x^2)). - Colin Barker, Sep 22 2018

Example

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

Crossrefs

Column 2 of A230840.

Sequence in context: A265864 A091169 A279380 * A270407 A000184 A007613

Adjacent sequences: A230832 A230833 A230834 * A230836 A230837 A230838

Keyword

nonn

Author

R. H. Hardin, Oct 31 2013

Status

approved