A221256 Number of 2 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no occupancy greater than 2.

0, 4, 8, 81, 392, 2500, 14112, 83521, 484128, 2829124, 16473800, 96059601, 559785800, 3262922884, 19017180288, 110841719041, 646029804672, 3765346202500, 21946028005832, 127910874833361, 745519107896648

Offset

1,2

Comments

Row 2 of A221255.

Links

R. H. Hardin, Table of n, a(n) for n = 1..41

Formula

Empirical: a(n) = 6*a(n-1) + 6*a(n-2) - 42*a(n-3) + 42*a(n-5) - 6*a(n-6) - 6*a(n-7) + a(n-8).

Empirical g.f.: x^2*(4 - 16*x + 9*x^2 + 26*x^3 - 2*x^4 - 6*x^5 + x^6) / ((1 - x)*(1 + x)*(1 - 6*x + x^2)*(1 + 2*x - x^2)*(1 - 2*x - x^2)). - Colin Barker, Aug 04 2018

Example

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

Crossrefs

Cf. A221255.

Sequence in context: A353032 A236284 A276979 * A068208 A090254 A222287

Adjacent sequences: A221253 A221254 A221255 * A221257 A221258 A221259

Keyword

nonn

Author

R. H. Hardin, Jan 06 2013

Status

approved