|
|
A228278
|
|
Number of n X 3 binary arrays with top left value 1 and no two ones adjacent horizontally, vertically or nw-se diagonally.
|
|
2
|
|
|
2, 3, 13, 35, 112, 337, 1034, 3154, 9637, 29431, 89895, 274564, 838609, 2561372, 7823242, 23894643, 72981777, 222909351, 680835436, 2079486057, 6351405998, 19399196250, 59251261117, 180972030923, 552745635451, 1688259428536
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
a(n) = a(n-1) + 5*a(n-2) + 4*a(n-3) - a(n-5).
G.f.: x*(2 + x - x^3) / ((1 + x)*(1 - 2*x - 3*x^2 - x^3 + x^4)). - Colin Barker, Mar 16 2018
|
|
EXAMPLE
|
Some solutions for n=4:
..1..0..0....1..0..0....1..0..0....1..0..1....1..0..0....1..0..1....1..0..0
..0..0..0....0..0..0....0..0..1....0..0..0....0..0..0....0..0..0....0..0..0
..0..0..1....0..0..0....0..0..0....0..0..0....1..0..0....0..0..1....0..1..0
..0..0..0....1..0..1....1..0..0....0..1..0....0..0..1....0..1..0....1..0..0
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|