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A221689 Number of n X 3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction. 1
6, 152, 3112, 63676, 1302720, 26650988, 545221260, 11154026300, 228186749552, 4668196767064, 95500991265668, 1953739262283024, 39969188300499044, 817681276128120100, 16727952148700884996, 342216938625170086928 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A221693.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 24*a(n-1) - 69*a(n-2) - 71*a(n-3) + 2*a(n-4) for n>5.

Empirical g.f.: 2*x*(3 + 4*x - 61*x^2 - 49*x^3 + 2*x^4) / (1 - 24*x + 69*x^2 + 71*x^3 - 2*x^4). - Colin Barker, Aug 10 2018

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A221693.

Sequence in context: A147796 A003766 A278728 * A319036 A185211 A046182

Adjacent sequences:  A221686 A221687 A221688 * A221690 A221691 A221692

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 22 2013

STATUS

approved

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Last modified August 9 01:08 EDT 2020. Contains 336309 sequences. (Running on oeis4.)