A221066 Sum of neighbor maps: number of n X 2 binary arrays indicating the locations of corresponding elements equal to the sum mod 4 of their king-move neighbors in a random 0..3 n X 2 array.

2, 8, 20, 56, 168, 476, 1364, 3952, 11360, 32692, 94236, 271352, 781432, 2250892, 6482724, 18670784, 53775312, 154880036, 446074860, 1284760776, 3700290152, 10657349244, 30694667380, 88404940816, 254618597952, 733337259924

Offset: 1

Author

R. H. Hardin, Dec 31 2012

Keywords

• nonn

Comments

Column 2 of A221072.

Examples

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

Links

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

Crossrefs

Cf. A221072.

Formula

Empirical: a(n) = 2*a(n-1) + 2*a(n-2) + 4*a(n-3) - 5*a(n-4) - 6*a(n-5).

Empirical g.f.: 2*x*(1 + x)*(1 + x - x^2 - 3*x^3) / (1 - 2*x - 2*x^2 - 4*x^3 + 5*x^4 + 6*x^5). - Colin Barker, Aug 03 2018