A207177 Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 0 1 0 vertically.

7, 49, 241, 1171, 5917, 30067, 151981, 767377, 3877045, 19592047, 98998267, 500220187, 2527540111, 12771357967, 64532102977, 326072549563, 1647603384079, 8325132536305, 42065847045655, 212553428463613, 1074005709153595

Offset: 1

Author

R. H. Hardin, Feb 15 2012

Keywords

• nonn

Comments

Column 3 of A207182.

Examples

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

Links

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

Crossrefs

Cf. A207182.

Formula

Empirical: a(n) = 4*a(n-1) + 2*a(n-2) + 12*a(n-3) + 23*a(n-4) + 6*a(n-5) - a(n-6) - 2*a(n-7) - a(n-8).

Empirical g.f.: x*(7 + 21*x + 31*x^2 + 25*x^3 + 2*x^4 - 4*x^5 - 3*x^6 - x^7) / (1 - 4*x - 2*x^2 - 12*x^3 - 23*x^4 - 6*x^5 + x^6 + 2*x^7 + x^8). - Colin Barker, Jun 21 2018