A232336 Number of 2 X n 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.

1, 6, 18, 32, 82, 162, 388, 806, 1858, 3968, 8962, 19426, 43396, 94822, 210578, 462112, 1022994, 2250178, 4972804, 10951878, 24180994, 53291008, 117604738, 259275842, 572028164, 1261360966, 2782483346, 6136209184, 13535050578, 29850527586

Offset: 1

Author

R. H. Hardin, Nov 22 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 2 of A232335.

Formula

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

Empirical g.f.: x*(1 + 5*x + 9*x^2 - 3*x^3 + x^4 - 3*x^5) / ((1 + x - x^2)*(1 - 2*x - x^3)). - Colin Barker, Oct 04 2018