A251337 Number of (n+1) X (2+1) 0..3 arrays with every 2 X 2 subblock summing to a nonzero multiple of 3.

455, 3315, 24714, 189129, 1487375, 12022920, 99776859, 848228679, 7364934770, 65097686685, 583829921739, 5297111776824, 48496766872295, 447087492211875, 4143325157339274, 38549110514055249, 359711119457800055

Offset

1,1

Links

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

Formula

Empirical: a(n) = 27*a(n-1) - 252*a(n-2) + 813*a(n-3) + 589*a(n-4) - 5250*a(n-5) - 2310*a(n-6) + 1764*a(n-7).

Empirical g.f.: x*(455 - 8970*x + 49869*x^2 - 12684*x^3 - 354270*x^4 - 131964*x^5 + 112896*x^6) / ((1 - 6*x)*(1 - 7*x)*(1 - 6*x - 6*x^2)*(1 - 8*x - 14*x^2 + 7*x^3)). - Colin Barker, Nov 29 2018

Example

Some solutions for n=4:
..0..3..0....1..2..0....0..3..3....0..0..2....0..3..3....0..3..3....1..2..0
..0..3..0....2..1..0....3..3..0....3..0..1....2..1..2....1..2..1....3..3..1
..0..3..0....0..0..2....3..0..0....3..0..2....3..3..0....1..2..1....3..0..2
..3..3..3....3..0..1....3..3..3....3..3..1....0..3..3....0..0..0....3..0..1
..2..1..2....3..0..2....2..1..2....3..0..2....0..0..0....0..3..0....2..1..1

Crossrefs

Column 2 of A251343.

Sequence in context: A324633 A260735 A241618 * A282232 A061544 A015276

Adjacent sequences: A251334 A251335 A251336 * A251338 A251339 A251340

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved