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.

0, 8, 50, 313, 1980, 12494, 78880, 497940, 3143384, 19843336, 125265720, 790768832, 4991910856, 31512587760, 198930468440, 1255794385648, 7927491165000, 50044112904464, 315914982635800, 1994286049109040, 12589389751704584

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 A357479

Adjacent sequences: A221475 A221476 A221477 * A221479 A221480 A221481

Keyword

nonn

Author

R. H. Hardin, Jan 17 2013

Status

approved