A238721 Number of n X 3 0..2 arrays with no element equal to the sum modulo 3 of elements to its left or elements above it.

4, 10, 40, 86, 336, 704, 2704, 5660, 21504, 45176, 170464, 359400, 1350272, 2854496, 10694912, 22650672, 84716224, 179637056, 671110848, 1424180800, 5316817088, 11288673952, 42124029504, 89466980000, 333750473152, 708999096096, 2644373950784, 5618300601952

Offset

1,1

Links

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

Formula

Empirical: a(n) = 17*a(n-2) -96*a(n-4) +210*a(n-6) -152*a(n-8).

Example

Some solutions for n=5:
..1..2..1....2..1..1....2..1..2....2..1..1....1..2..1....1..2..1....2..1..1
..2..1..2....1..0..2....1..2..1....1..2..2....2..0..0....2..0..0....1..2..2
..1..2..1....2..0..1....1..2..2....1..2..2....2..0..0....1..0..2....2..1..1
..2..0..0....1..0..2....2..0..1....2..1..1....1..0..2....2..0..1....1..0..2
..2..1..2....1..2..1....2..1..2....1..2..1....2..0..1....2..1..2....1..0..2

Crossrefs

Column 3 of A238726.

Sequence in context: A038168 A186337 A100307 * A077811 A136855 A136860

Adjacent sequences: A238718 A238719 A238720 * A238722 A238723 A238724

Keyword

nonn

Author

R. H. Hardin, Mar 03 2014

Status

approved