|
|
A207840
|
|
Number of n X 3 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 1 1 1 vertically.
|
|
4
|
|
|
6, 36, 72, 240, 704, 2080, 6216, 18496, 55000, 163760, 487296, 1450192, 4315896, 12844160, 38224536, 113757504, 338545344, 1007520656, 2998410360, 8923354336, 26556156776, 79031879392, 235201123584, 699965244000, 2083116504872
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
Empirical: a(n) = a(n-1) + 4*a(n-2) + 5*a(n-3) + 2*a(n-4) - a(n-5) + a(n-6) for n>8.
Empirical g.f.: 2*x*(3 + 15*x + 6*x^2 - 3*x^3 - 8*x^4 - 5*x^5 + 3*x^6 - 2*x^7) / (1 - x - 4*x^2 - 5*x^3 - 2*x^4 + x^5 - x^6). - Colin Barker, Feb 21 2018
|
|
EXAMPLE
|
Some solutions for n=4:
..1..1..1....0..1..1....1..1..0....1..1..0....1..0..1....0..1..0....0..1..1
..1..0..1....1..0..1....1..0..1....1..0..0....1..0..0....0..1..0....1..0..0
..0..1..0....0..1..0....0..1..1....0..1..1....0..1..0....1..0..1....1..0..1
..0..1..1....1..1..1....0..1..0....1..1..0....1..0..1....0..1..1....0..1..0
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|