A209729 1/4 the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having distinct edge sums.

22, 124, 696, 3912, 21976, 123480, 693752, 3897880, 21900088, 123045592, 691329528, 3884227224, 21823477432, 122614931544, 688910387576, 3870634114072, 21747107494456, 122185841630680, 686499566270712

Offset: 1

Author

R. H. Hardin, Mar 12 2012

Keywords

• nonn

Comments

Column 1 of A209736.

Examples

			Some solutions for n=4:
..3..1....1..0....1..2....1..3....1..2....0..0....2..1....1..3....1..0....1..1
..2..0....1..3....0..2....0..2....3..3....1..2....2..0....0..2....1..3....3..2
..1..0....2..3....3..2....3..2....1..2....1..3....1..0....3..2....0..2....0..0
..1..3....1..1....3..0....1..0....0..0....0..2....1..3....3..0....1..2....3..1
..0..2....0..3....2..0....1..3....1..3....0..1....2..3....3..1....1..3....2..0
		

Links

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

Crossrefs

Cf. A209736.

Formula

Empirical: a(n) = 3*a(n-1) + 14*a(n-2) + 4*a(n-3).

Empirical g.f.: 2*x*(11 + 29*x + 8*x^2) / (1 - 3*x - 14*x^2 - 4*x^3). - Colin Barker, Jul 12 2018