A202796 Number of n X 2 binary arrays with every one adjacent to another one horizontally or vertically.

2, 10, 36, 126, 454, 1632, 5854, 21010, 75412, 270662, 971438, 3486624, 12513958, 44914250, 161203204, 578579694, 2076599286, 7453190368, 26750489166, 96011055010, 344596415668, 1236802258678, 4439047411742, 15932330156576

Offset: 1

Author

R. H. Hardin, Dec 24 2011

Keywords

• nonn

Comments

Column 2 of A202802.

Examples

			Some solutions for n=5:
..0..1....0..0....0..1....1..0....0..0....1..0....1..1....0..1....0..1....1..0
..0..1....1..0....1..1....1..0....0..0....1..0....1..1....1..1....1..1....1..1
..1..1....1..1....1..1....1..1....0..1....0..0....1..0....0..0....1..0....0..1
..1..1....0..1....1..0....1..0....0..1....0..1....0..1....1..0....0..0....1..0
..1..0....1..1....1..0....1..0....0..0....0..1....1..1....1..1....0..0....1..0
		

Links

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

Crossrefs

Cf. A202802.

Formula

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

Empirical g.f.: 2*x*(1 + 2*x + 2*x^2) / (1 - 3*x - x^2 - 4*x^3). - Colin Barker, Feb 20 2018