A232508 Number of (n+1) X (1+1) 0..2 arrays with every element next to itself plus and minus one within the range 0..2 horizontally, diagonally or antidiagonally, with no adjacent elements equal.

4, 4, 8, 16, 28, 52, 96, 176, 324, 596, 1096, 2016, 3708, 6820, 12544, 23072, 42436, 78052, 143560, 264048, 485660, 893268, 1642976, 3021904, 5558148, 10223028, 18803080, 34584256, 63610364, 116997700, 215192320, 395800384, 727990404

Offset

1,1

Links

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

Formula

Empirical: a(n) = a(n-1) + a(n-2) + a(n-3).

Empirical g.f.: 4*x / (1 - x - x^2 - x^3). - Colin Barker, Oct 05 2018

Example

Some solutions for n=7:
..1..0....0..1....1..0....1..0....0..1....2..1....0..1....1..0....0..1....0..1
..1..2....2..1....1..2....1..2....2..1....0..1....2..1....1..2....2..1....2..1
..1..0....2..1....1..0....1..0....2..0....0..1....2..1....1..2....0..1....0..1
..1..2....0..1....1..2....1..2....1..0....2..1....0..1....1..0....2..1....0..2
..1..0....2..1....1..0....1..2....1..2....0..1....0..1....1..0....2..1....1..2
..1..2....0..1....1..2....1..0....1..2....0..1....2..1....1..2....0..1....1..0
..1..2....0..1....1..0....1..0....1..0....2..1....0..1....1..0....2..1....1..0
..1..0....2..1....1..2....1..2....1..2....0..1....2..1....1..2....0..1....1..2

Crossrefs

Column 1 of A232515.

Sequence in context: A030168 A261212 A112435 * A028610 A019171 A038551

Adjacent sequences: A232505 A232506 A232507 * A232509 A232510 A232511

Keyword

nonn

Author

R. H. Hardin, Nov 25 2013

Status

approved