A221313 Square root of number of nX4 arrays of occupancy after each element moves to some horizontal or vertical neighbor, with every occupancy equal to zero or two

1, 4, 9, 23, 57, 142, 353, 878, 2183, 5428, 13496, 33556, 83432, 207441, 515770, 1282382, 3188443

Offset

1,2

Comments

Column 4 of A221314

Links

Table of n, a(n) for n=1..17.

Formula

Empirical: a(n) = 2*a(n-1) + 2*a(n-2) - a(n-3) - 2*a(n-4) - a(n-5). - Vaclav Kotesovec, May 23 2013

Example

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

Crossrefs

Sequence in context: A014543 A343676 A131607 * A238832 A192473 A027119

Adjacent sequences: A221310 A221311 A221312 * A221314 A221315 A221316

Keyword

nonn

Author

R. H. Hardin Jan 10 2013

Status

approved