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A221478 Number of n X 3 arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction. 1
0, 8, 50, 313, 1980, 12494, 78880, 497940, 3143384, 19843336, 125265720, 790768832, 4991910856, 31512587760, 198930468440, 1255794385648, 7927491165000, 50044112904464, 315914982635800, 1994286049109040, 12589389751704584 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 3 of A221483.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..66

FORMULA

Empirical: a(n) = 8*a(n-1) - 7*a(n-2) - 24*a(n-3) + 6*a(n-4) for n>6.

Empirical g.f.: x^2*(8 - 14*x - 31*x^2 + 18*x^3 - 3*x^4) / (1 - 8*x + 7*x^2 + 24*x^3 - 6*x^4). - Colin Barker, Aug 05 2018

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A221483.

Sequence in context: A037547 A061801 A240050 * A287812 A180029 A133129

Adjacent sequences:  A221475 A221476 A221477 * A221479 A221480 A221481

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 17 2013

STATUS

approved

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Last modified June 1 04:57 EDT 2020. Contains 334758 sequences. (Running on oeis4.)