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

1,2

Comments

Column 3 of A183328

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

Example

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

Crossrefs

Sequence in context: A091714 A017991 A065614 * A058356 A270048 A295719

Adjacent sequences: A183321 A183322 A183323 * A183325 A183326 A183327

Keyword

nonn

Author

R. H. Hardin Jan 03 2011

Status

approved