A221415 Number of n X 4 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, with every occupancy equal to zero or two.

4, 29, 226, 1766, 13794, 107695, 840673, 6561928, 51218473, 399777826, 3120396286, 24355691434, 190103915555, 1483821378069, 11581696324348, 90398811127357, 705591374468222, 5507364322727938, 42986724144662890, 335525006918408343

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..90

Formula

Empirical: a(n) = 10*a(n-1) - 15*a(n-2) - 19*a(n-3) + 17*a(n-4) + 12*a(n-5) - a(n-6) + a(n-7).

Empirical g.f.: x*(4 - 11*x - 4*x^2 + 17*x^3 + 7*x^4 - 2*x^5 + x^6) / (1 - 10*x + 15*x^2 + 19*x^3 - 17*x^4 - 12*x^5 + x^6 - x^7). - Colin Barker, Aug 05 2018

Example

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

Crossrefs

Column 4 of A221419.

Sequence in context: A135429 A079756 A344098 * A087809 A140526 A151343

Adjacent sequences: A221412 A221413 A221414 * A221416 A221417 A221418

Keyword

nonn

Author

R. H. Hardin, Jan 15 2013

Status

approved