A221667 Sum of neighbor maps: number of 2 X n binary arrays indicating the locations of corresponding elements equal to the sum mod 3 of their horizontal, diagonal and antidiagonal neighbors in a random 0..2 2 X n array.

4, 12, 64, 256, 992, 4096, 16384, 65344, 262144, 1048576, 4193280, 16777216, 67108864, 268430336, 1073741824, 4294967296, 17179844608, 68719476736, 274877906944, 1099511513088, 4398046511104, 17592186044416, 70368743653376

Offset: 1

Author

R. H. Hardin, Jan 21 2013

Keywords

• nonn

Comments

Row 2 of A221666.

Examples

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

Links

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

Crossrefs

Cf. A221666.

Formula

Empirical: a(n) = 4*a(n-1) + 8*a(n-3) - 32*a(n-4) - 16*a(n-6) + 64*a(n-7).

Empirical g.f.: 4*x*(1 - x + 4*x^2 - 8*x^3 + 16*x^6) / ((1 - 4*x)*(1 - 4*x^3)^2). - Colin Barker, Aug 10 2018