|
| |
|
|
A278151
|
|
Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) (1,-1) or (1,0), with upper left element zero.
|
|
1
|
|
|
|
0, 2, 7, 22, 75, 254, 859, 2906, 9831, 33258, 112511, 380622, 1287635, 4356038, 14736371, 49852786, 168650767, 570541458, 1930127927, 6529576006, 22089397403, 74727896142, 252802661835, 855225279050, 2893206395127, 9787647126266
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
LINKS
|
|
|
|
FORMULA
|
Empirical: a(n) = 3*a(n-1) + a(n-2) + a(n-3) for n>4.
Empirical g.f.: x^2*(2 - x)*(1 + x) / (1 - 3*x - x^2 - x^3). - Colin Barker, Feb 07 2019
|
|
|
EXAMPLE
|
Some solutions for n=4:
..0..1. .0..0. .0..0. .0..0. .0..0. .0..1. .0..1. .0..0. .0..0. .0..1
..0..1. .1..1. .1..1. .1..0. .1..1. .0..1. .0..1. .1..1. .1..1. .0..1
..1..0. .1..0. .1..0. .1..1. .0..1. .0..1. .1..0. .0..0. .1..0. .0..0
..0..1. .0..1. .0..0. .0..0. .0..0. .1..0. .1..0. .1..1. .1..0. .1..1
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
|
|
|
STATUS
|
approved
|
| |
|
|
