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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. 1
0, 4, 8, 81, 392, 2500, 14112, 83521, 484128, 2829124, 16473800, 96059601, 559785800, 3262922884, 19017180288, 110841719041, 646029804672, 3765346202500, 21946028005832, 127910874833361, 745519107896648 (list; graph; refs; listen; history; text; internal format)
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: A288956 A236284 A276979 * A068208 A090254 A222287

Adjacent sequences:  A221253 A221254 A221255 * A221257 A221258 A221259

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 06 2013

STATUS

approved

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Last modified October 25 09:51 EDT 2021. Contains 348239 sequences. (Running on oeis4.)