A208496 Number of n X 3 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 0 and 1 1 1 vertically.

6, 36, 60, 126, 234, 456, 896, 1722, 3360, 6512, 12642, 24570, 47644, 92568, 179690, 348800, 677340, 1314846, 2552850, 4956336, 9622272, 18681842, 36269696, 70416640, 136712226, 265421170, 515308500, 1000454184, 1942349698, 3771013664

Offset: 1

Author

R. H. Hardin, Feb 27 2012

Keywords

• nonn

Comments

Column 3 of A208501.

Examples

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

Links

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

Crossrefs

Cf. A208501.

Formula

Empirical: a(n) = a(n-2) + 4*a(n-3) + 2*a(n-4) + 2*a(n-5) - 2*a(n-6) + a(n-7) + a(n-9) for n>11.

Empirical g.f.: 2*x*(3 + 18*x + 27*x^2 + 33*x^3 + 9*x^4 + 3*x^5 - 11*x^6 + 12*x^7 + 2*x^8 + 6*x^9 - 2*x^10) / (1 - x^2 - 4*x^3 - 2*x^4 - 2*x^5 + 2*x^6 - x^7 - x^9). - Colin Barker, Mar 06 2018