|
|
A221769
|
|
Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor, without move-in move-out left turns.
|
|
1
|
|
|
3, 27, 240, 2127, 18828, 166581, 1473549, 13033908, 115285587, 1019699649, 9019211256, 79774585647, 705603080553, 6241031204616, 55201672045839, 488256584905473, 4318609990477032, 38197932848425719, 337859190101460441
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
Empirical: a(n) = 15*a(n-1) - 67*a(n-2) + 120*a(n-3) - 80*a(n-4) + 10*a(n-5).
Empirical g.f.: 3*x*(1 - x)*(1 - 5*x + 7*x^2 - x^3) / (1 - 15*x + 67*x^2 - 120*x^3 + 80*x^4 - 10*x^5). - Colin Barker, Aug 10 2018
|
|
EXAMPLE
|
Some solutions for n=3:
..1..0....1..0....0..1....2..1....0..2....0..1....0..1....2..1....0..3....1..1
..0..3....2..2....2..2....2..0....1..0....0..3....2..1....0..0....1..1....1..2
..1..1....0..1....0..1....0..1....2..1....2..0....1..1....0..3....1..0....0..1
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|