A230331 Number of n X 2 0..2 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value (x(i,j)+1) mod 3, and upper left element zero.

0, 6, 34, 218, 1386, 8810, 56010, 356074, 2263690, 14391082, 91489226, 581629546, 3697625866, 23507122602, 149443138122, 950063174890, 6039889469834, 38397725300778, 244107994962122, 1551881335096170, 9865861536380938

Offset

1,2

Links

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

Formula

Empirical: a(n) = 5*a(n-1) + 8*a(n-2) + 4*a(n-3).

Empirical g.f.: 2*x^2*(3 + 2*x) / (1 - 5*x - 8*x^2 - 4*x^3). - Colin Barker, Sep 21 2018

Example

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

Crossrefs

Column 2 of A230337.

Sequence in context: A184185 A216317 A370324 * A267242 A197436 A334787

Adjacent sequences: A230328 A230329 A230330 * A230332 A230333 A230334

Keyword

nonn

Author

R. H. Hardin, Oct 16 2013

Status

approved