A221587 Equals one maps: number of n X 2 binary arrays indicating the locations of corresponding elements equal to exactly one of their king-move neighbors in a random 0..3 n X 2 array.

2, 8, 40, 180, 772, 3264, 13634, 56456, 232150, 949520, 3867132, 15696660, 63539998, 256648344, 1034811554, 4166389484, 16755205300, 67316907560, 270245535066, 1084211943720, 4347515085838, 17425292086536, 69817530875564

Offset

1,1

Comments

Column 2 of A221590.

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 3*a(n-2) - 22*a(n-3) + 7*a(n-4) + 4*a(n-5) for n>8.

Empirical g.f.: 2*x*(1 - 2*x - x^2 + 4*x^3 - 13*x^4 - 6*x^5 + 7*x^6 + 4*x^7) / ((1 - 4*x)*(1 + x - x^2)*(1 - 3*x - x^2)). - Colin Barker, Aug 08 2018

Example

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

Crossrefs

Cf. A221590.

Sequence in context: A181326 A220964 A231125 * A186947 A071007 A027617

Adjacent sequences: A221584 A221585 A221586 * A221588 A221589 A221590

Keyword

nonn

Author

R. H. Hardin, Jan 20 2013

Status

approved