A183624 Number of (n+1) X 2 0..2 arrays with every 2 x 2 subblock summing to 4.

19, 45, 115, 309, 859, 2445, 7075, 20709, 61099, 181245, 539635, 1610709, 4815739, 14414445, 43177795, 129402309, 387944779, 1163310045, 3488881555, 10464547509, 31389448219, 94159956045, 282463090915, 847355718309, 2542000046059

Offset

1,1

Comments

Column 1 of A183632.

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3).

Conjectures from Colin Barker, Feb 22 2018: (Start)

G.f.: x*(19 - 69*x + 54*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).

a(n) = 2 + 2^(2+n) + 3^(1+n).

(End)

Example

Some solutions for 3 X 2:
..2..0....2..0....1..2....2..0....1..0....0..2....2..1....0..2....2..0....0..2
..2..0....1..1....1..0....0..2....1..2....0..2....0..1....1..1....2..0....2..0
..2..0....2..0....2..1....1..1....0..1....1..1....1..2....1..1....1..1....0..2

Crossrefs

Cf. A183632.

Sequence in context: A183632 A359558 A245864 * A378361 A115249 A325451

Adjacent sequences: A183621 A183622 A183623 * A183625 A183626 A183627

Keyword

nonn

Author

R. H. Hardin, Jan 06 2011

Status

approved