A232331 Number of nX4 0..2 arrays with every 0 next to a 1 and every 1 next to a 2 horizontally or antidiagonally, with no adjacent elements equal.

6, 32, 154, 734, 3472, 16338, 76630, 358656, 1676330, 7828014, 36533360, 170436130, 794923238, 3706958560, 17284778298, 80589690622, 375729468240, 1751693001458, 8166429157878, 38071572583616, 177486683779786, 827424427937102

Offset: 1

Author

R. H. Hardin, Nov 22 2013

Keywords

• nonn

Comments

Column 4 of A232335

Examples

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

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) -8*a(n-3) -4*a(n-4).

Empirical: G.f.: -2*x*(-3+5*x+8*x^2+4*x^3) / ( 1-7*x+9*x^2+8*x^3+4*x^4 ). - R. J. Mathar, Nov 24 2013