A240513 Number of n X 2 0..1 arrays with no element equal to exactly two horizontal and vertical neighbors, with new values 0..1 introduced in row major order.

2, 3, 6, 10, 21, 42, 86, 179, 370, 770, 1601, 3330, 6930, 14419, 30006, 62442, 129941, 270410, 562726, 1171043, 2436962, 5071362, 10553601, 21962242, 45703842, 95110563, 197926886, 411889610, 857150101, 1783745642, 3712008566, 7724760339

Offset: 1

Author

R. H. Hardin, Apr 06 2014

Keywords

• nonn

Comments

Column 2 of A240519.

Examples

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

Links

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

Crossrefs

Cf. A240519.

Formula

Empirical: a(n) = 2*a(n-1) + a(n-2) - a(n-3) - 2*a(n-4) + a(n-5).

Empirical g.f.: x*(2 - x)*(1 - x^2 - 2*x^3) / ((1 - x)*(1 - x - 2*x^2 - x^3 + x^4)). - Colin Barker, Feb 24 2018

Empirical: a(n) = 1+A105309(n). - R. J. Mathar, Nov 09 2018