A220324 Equals two maps: number of n X 3 binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal and antidiagonal neighbors in a random 0..1 n X 3 array.

2, 16, 92, 508, 2788, 15316, 84196, 462940, 2545492, 13996468, 76959844, 423164812, 2326777444, 12793817140, 70346976484, 386803802332, 2126845944052, 11694491219668, 64302318307108, 353567167818892, 1944093859291588

Offset

1,1

Comments

Column 3 of A220328.

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 9*a(n-2) + 3*a(n-3) + 6*a(n-4).

Empirical g.f.: 2*x*(1 + x - x^2 + x^3) / (1 - 7*x + 9*x^2 - 3*x^3 - 6*x^4). - Colin Barker, Jul 31 2018

Example

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

Crossrefs

Cf. A220328.

Sequence in context: A208550 A214824 A317451 * A208002 A220932 A207558

Adjacent sequences: A220321 A220322 A220323 * A220325 A220326 A220327

Keyword

nonn

Author

R. H. Hardin, Dec 10 2012

Status

approved