A205249 Number of (n+1) X 3 0..1 arrays with the number of clockwise edge increases in every 2 X 2 subblock the same.

40, 168, 752, 3416, 15568, 71000, 323856, 1477272, 6738640, 30738648, 140215952, 639602456, 2917580368, 13308696920, 60708323856, 276924225432, 1263204479440, 5762173946328, 26284460772752, 119897955971096, 546920858309968

Offset: 1

Author

R. H. Hardin, Jan 24 2012

Keywords

• nonn

Comments

Column 2 of A205255.

Examples

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

Links

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

Crossrefs

Cf. A205255.

Formula

Empirical: a(n) = 6*a(n-1) -7*a(n-2) +2*a(n-3).

Empirical g.f.: 8*x*(5 - 9*x + 3*x^2) / ((1 - x)*(1 - 5*x + 2*x^2)). - Colin Barker, Jun 11 2018