A208264 Number of n X 3 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than two of its immediate leftward or upward or left-upward diagonal neighbors.

4, 25, 161, 1033, 6631, 42563, 273205, 1753657, 11256431, 72253147, 463780861, 2976931745, 19108426759, 122653794067, 787294181189, 5053509615817, 32437632650335, 208211736387083, 1336476297041869, 8578617726111793

Offset: 1

Author

R. H. Hardin, Feb 24 2012

Keywords

• nonn

Comments

Column 3 of A208269.

Examples

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

Links

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

Crossrefs

Cf. A208269.

Formula

Empirical: a(n) = 6*a(n-1) + 3*a(n-2) - 2*a(n-3).

Empirical g.f.: x*(4 + x - x^2) / (1 - 6*x - 3*x^2 + 2*x^3). - Colin Barker, Jun 29 2018