A251319 Number of (n+1) X (1+1) 0..1 arrays with every 2 X 2 subblock having one or two 1s.

10, 28, 78, 220, 618, 1740, 4894, 13772, 38746, 109020, 306734, 863036, 2428234, 6832108, 19222846, 54085548, 152175418, 428161788, 1204678734, 3389491996, 9536696618, 26832511756, 75496129374, 212416400780, 597656166170

Offset

1,1

Links

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

Formula

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

Empirical g.f.: 2*x*(5 + 4*x - 4*x^2) / (1 - 2*x - 3*x^2 + 2*x^3). - Colin Barker, Nov 28 2018

Example

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

Crossrefs

Column 1 of A251326.

Sequence in context: A048491 A124703 A333241 * A126364 A076712 A116973

Adjacent sequences: A251316 A251317 A251318 * A251320 A251321 A251322

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved