A230658 Number of nX3 0..2 black 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, 15, 21, 135, 177, 1155, 1509, 9855, 12873, 84075, 109821, 717255, 936897, 6118995, 7992789, 52201935, 68187513, 445341435, 581716461, 3799265175, 4962698097, 32412020835, 42337417029, 276511126815, 361185960873

Offset

1,2

Comments

Column 3 of A230661

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*(-1-5*x+2*x^2) / ( 1-9*x^2+4*x^4 ). - R. J. Mathar, Oct 27 2013

Example

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

Crossrefs

Sequence in context: A076825 A259745 A118565 * A117801 A347303 A277585

Adjacent sequences: A230655 A230656 A230657 * A230659 A230660 A230661

Keyword

nonn

Author

R. H. Hardin, Oct 27 2013

Status

approved