A230647 Number of nX3 0..2 white square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value 2-x(i,j)

0, 3, 3, 21, 27, 177, 231, 1509, 1971, 12873, 16815, 109821, 143451, 936897, 1223799, 7992789, 10440387, 68187513, 89068287, 581716461, 759853035, 4962698097, 6482404167, 42337417029, 55302225363, 361185960873, 471790411599

Offset

1,2

Comments

Column 3 of A230652

Links

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

Formula

Empirical: a(n) = 9*a(n-2) -4*a(n-4).

Empirical: G.f. -3*x^2*(2*x+1)*(x-1) / ( 1-9*x^2+4*x^4 ). - R. J. Mathar, Oct 27 2013

Example

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

Crossrefs

Sequence in context: A205452 A159910 A172485 * A130723 A369078 A209528

Adjacent sequences: A230644 A230645 A230646 * A230648 A230649 A230650

Keyword

nonn

Author

R. H. Hardin, Oct 27 2013

Status

approved