A230648 Number of nX4 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, 9, 21, 123, 531, 2547, 11745, 54957, 255753, 1192623, 5557191, 25901847, 120714693, 562609041, 2622085629, 12220512675, 56954899323, 265444104699, 1237128910377, 5765764156725, 26871924749169, 125239314486231

Offset: 1

Author

R. H. Hardin, Oct 27 2013

Keywords

• nonn

Comments

Column 4 of A230652

Examples

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

Links

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

Formula

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

Empirical: G.f. 3*x^2*(1+x)*(x^2-5*x+3) / ( 1-3*x-8*x^2+x^3+x^4 ). - R. J. Mathar, Oct 27 2013