A230814 Number of nX3 0..2 arrays x(i,j) with each element horizontally or vertically next to at least one element with value (x(i,j)+1) mod 3 and at least one element with value (x(i,j)-1) mod 3, and upper left element zero

0, 2, 4, 12, 100, 326, 2114, 9226, 47220, 233480, 1135788, 5678402, 27785526, 137642146, 678271020, 3346581344, 16519160048, 81474120774, 402103867046, 1983757394910, 9788422760352, 48296742499360, 238296850975076

Offset

1,2

Comments

Column 3 of A230819

Links

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

Formula

Empirical: a(n) = 6*a(n-1) -2*a(n-2) -19*a(n-3) -a(n-4) +169*a(n-5) -607*a(n-6) +913*a(n-7) -1279*a(n-8) +2352*a(n-9) -3003*a(n-10) +3418*a(n-11) -2775*a(n-12) +1279*a(n-13) -676*a(n-14) +156*a(n-15) -4*a(n-16) -62*a(n-17) +60*a(n-18) -12*a(n-19)

Example

Some solutions for n=4
..0..1..2....0..2..1....0..2..1....0..1..2....0..1..2....0..2..1....0..1..2
..2..1..0....1..2..0....1..2..0....2..1..0....2..1..0....1..2..0....2..1..0
..2..1..0....1..2..0....1..0..2....0..1..2....1..0..2....0..2..1....0..2..1
..0..1..2....0..2..1....2..0..1....2..1..0....2..0..1....1..2..0....1..2..0

Crossrefs

Sequence in context: A228809 A326945 A309718 * A325502 A038791 A327563

Adjacent sequences: A230811 A230812 A230813 * A230815 A230816 A230817

Keyword

nonn

Author

R. H. Hardin, Oct 30 2013

Status

approved