A221796 Number of n X 3 arrays of occupancy after each element moves to some horizontal or vertical neighbor, without move-in move-out straight through or left turns.

0, 12, 12, 207, 470, 4073, 13314, 85974, 338148, 1892213, 8198076, 42661873, 194441436, 974764224, 4561903748, 22432271947, 106441266034, 518196714761, 2476544809950, 11994439907546, 57537238641980, 277917546512145

Offset

1,2

Comments

Column 3 of A221800.

Links

R. H. Hardin, Table of n, a(n) for n = 1..90

Formula

Empirical: a(n) = 27*a(n-2) + 14*a(n-3) - 165*a(n-4) - 20*a(n-5) + 329*a(n-6) - 48*a(n-7) - 131*a(n-8) - 34*a(n-9) + 9*a(n-10).

Empirical g.f.: x^2*(12 + 12*x - 117*x^2 - 22*x^3 + 296*x^4 - 54*x^5 - 130*x^6 - 34*x^7 + 9*x^8) / (1 - 27*x^2 - 14*x^3 + 165*x^4 + 20*x^5 - 329*x^6 + 48*x^7 + 131*x^8 + 34*x^9 - 9*x^10). - Colin Barker, Aug 11 2018

Example

Some solutions for n=3:
..1..1..1....0..1..1....0..2..0....1..1..1....0..2..1....1..1..1....1..2..1
..1..0..2....2..2..1....1..2..1....1..0..1....1..1..1....1..2..1....1..0..1
..1..1..1....0..1..1....1..1..1....1..2..1....1..1..1....0..2..0....1..1..1

Crossrefs

Cf. A221800.

Sequence in context: A178341 A165833 A038338 * A222298 A122253 A156456

Adjacent sequences: A221793 A221794 A221795 * A221797 A221798 A221799

Keyword

nonn

Author

R. H. Hardin, Jan 26 2013

Status

approved