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A221694 Number of 2 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction. 1
1, 21, 152, 1336, 11036, 92660, 774380, 6479664, 54200980, 453418640, 3792991120, 31729761276, 265430689860, 2220422566716, 18574626389432, 155383375746468, 1299837358873328, 10873603138412824, 90961568659281764, 760925966163564220 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 2 of A221693.

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) + 28*a(n-2) + 9*a(n-3) - 62*a(n-4) - 30*a(n-5) + 64*a(n-6) + 32*a(n-7) - 32*a(n-8) + 32*a(n-9).

Empirical g.f.: x*(1 + 16*x + 19*x^2 - 21*x^3 - 27*x^4 + 36*x^5 + 38*x^6 - 24*x^7 + 24*x^8) / ((1 + 2*x)^2*(1 - 9*x + 4*x^2 + 11*x^3 + 2*x^4 - 22*x^5 + 16*x^6 - 8*x^7)). - Colin Barker, Aug 10 2018

EXAMPLE

Some solutions for n=3:

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

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

CROSSREFS

Cf. A221693.

Sequence in context: A241697 A239569 A219599 * A229262 A184376 A184368

Adjacent sequences: A221691 A221692 A221693 * A221695 A221696 A221697

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 22 2013

STATUS

approved

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Last modified January 28 02:10 EST 2023. Contains 359849 sequences. (Running on oeis4.)