A251336 Number of (n+1) X (1+1) 0..3 arrays with every 2 X 2 subblock summing to a nonzero multiple of 3.

85, 455, 2450, 13275, 72375, 397000, 2190625, 12156875, 67831250, 380409375, 2143546875, 12131500000, 68933828125, 393119609375, 2249232031250, 12906582421875, 74253193359375, 428169484375000, 2473966416015625

Offset

1,1

Links

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

Formula

Empirical: a(n) = 10*a(n-1) - 20*a(n-2) - 25*a(n-3).

Empirical g.f.: 5*x*(17 - 79*x - 80*x^2) / ((1 - 5*x)*(1 - 5*x - 5*x^2)). - Colin Barker, Nov 29 2018

Example

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

Crossrefs

Column 1 of A251343.

Sequence in context: A297399 A020212 A251343 * A262425 A264425 A250463

Adjacent sequences: A251333 A251334 A251335 * A251337 A251338 A251339

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved