A183324 Number of nX3 binary arrays with each 1 adjacent to exactly two other 1s.

1, 3, 6, 10, 19, 37, 69, 129, 244, 460, 865, 1629, 3069, 5779, 10882, 20494, 38595, 72681, 136873, 257761, 485416, 914136, 1721505, 3241945, 6105241, 11497411, 21651966, 40775058, 76787731, 144606925, 272324269, 512842017, 965785884

Offset: 1

Author

R. H. Hardin Jan 03 2011

Keywords

• nonn

Comments

Column 3 of A183328

Examples

			All solutions for 4X3
..0..0..0....0..0..0....1..1..1....0..0..0....0..0..0....0..0..0....1..1..0
..0..0..0....0..0..0....1..0..1....1..1..1....0..1..1....1..1..0....1..1..0
..1..1..0....0..0..0....1..0..1....1..0..1....0..1..1....1..1..0....0..0..0
..1..1..0....0..0..0....1..1..1....1..1..1....0..0..0....0..0..0....0..0..0
...
..0..0..0....0..1..1....1..1..1
..0..0..0....0..1..1....1..0..1
..0..1..1....0..0..0....1..1..1
..0..1..1....0..0..0....0..0..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

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

Empirical: G.f. -x*(-1-x+x^3-x^2) / ( 1-2*x+x^2-2*x^3+x^4 ), see A033305 - R. J. Mathar, Sep 27 2013