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A221089 Number of 3 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor. 1
0, 16, 270, 6889, 154440, 3538161, 80655102, 1840667409, 41995876248, 958215843225, 21863225325726, 498845926549881, 11381993364572136, 259699010088371841, 5925462372979055550, 135199223931709452321 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 3 of A221087.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..34

FORMULA

Empirical: a(n) = 24*a(n-1) - 648*a(n-3) + 729*a(n-4) for n>7.

Empirical g.f.: x^2*(16 - 114*x + 409*x^2 - 528*x^3 - 5103*x^4 + 6480*x^5) / ((1 - 24*x + 27*x^2)*(1 - 27*x^2)). - Colin Barker, Aug 03 2018

EXAMPLE

Some solutions for n=3:

..1..2..0....0..1..0....0..1..0....0..2..0....1..1..0....0..1..1....1..2..0

..0..2..0....1..2..2....1..3..1....2..2..1....0..4..1....0..4..0....0..2..0

..2..2..0....0..3..0....1..2..0....0..2..0....1..1..0....2..1..0....1..2..1

CROSSREFS

Cf. A221087.

Sequence in context: A218062 A220757 A166908 * A119290 A161595 A144660

Adjacent sequences:  A221086 A221087 A221088 * A221090 A221091 A221092

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 01 2013

STATUS

approved

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Last modified January 25 22:06 EST 2022. Contains 350572 sequences. (Running on oeis4.)