VOOZH about

URL: https://oeis.org/A251319

⇱ A251319 - OEIS

login
A251319
Number of (n+1) X (1+1) 0..1 arrays with every 2 X 2 subblock having one or two 1s.
1
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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 01 2014
STATUS
approved