A207437 Number of n X 3 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 0 1 and 1 0 0 vertically.

6, 36, 108, 333, 1144, 4048, 14743, 54250, 201098, 747683, 2785178, 10383774, 38732585, 144511028, 539243500, 2012324661, 7509786472, 28026278000, 104594259855, 390348614698, 1456795959866, 5436826706395, 20290493971290

Offset: 1

Author

R. H. Hardin, Feb 17 2012

Keywords

• nonn

Comments

Column 3 of A207442.

Examples

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

Links

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

Crossrefs

Cf. A207442.

Formula

Empirical: a(n) = 6*a(n-1) - 5*a(n-2) - 22*a(n-3) + 32*a(n-4) + 16*a(n-5) - 35*a(n-6) + 2*a(n-7) + 9*a(n-8) - 2*a(n-9) for n>10.

Empirical g.f.: x*(6 - 78*x^2 - 3*x^3 + 286*x^4 - 23*x^5 - 321*x^6 + 64*x^7 + 87*x^8 - 22*x^9) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - 4*x + x^2)*(1 + x - x^2)*(1 - x - x^2)). - Colin Barker, Jun 22 2018