|
|
A211479
|
|
Number of -1..1 arrays x(i) of n+1 elements i=1..n+1 with x(i)+x(j), x(i+1)+x(j+1), -(x(i)+x(j+1)), and -(x(i+1)+x(j)) having two, three or four distinct values for every i<=n and j<=n.
|
|
1
|
|
|
8, 22, 58, 150, 382, 962, 2402, 5958, 14702, 36130, 88498, 216198, 527038, 1282562, 3116738, 7565190, 18345422, 44452642, 107643922, 260526918, 630270622, 1524213890, 3684989858, 8906776518, 21523708718, 52004525602, 125633423218
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
FORMULA
|
Empirical: a(n) = 4*a(n-1) - 3*a(n-2) - 2*a(n-3).
G.f.: 2*x*(4 - 5*x - 3*x^2) / ((1 - 2*x)*(1 - 2*x - x^2)).
a(n) = -3*2^n + (3-2*sqrt(2))*(1-sqrt(2))^n + (1+sqrt(2))^n*(3+2*sqrt(2)).
(End)
|
|
EXAMPLE
|
Some solutions for n=5:
..1...-1....1...-1....0....1....1...-1...-1...-1...-1....1....0...-1....1....0
..1....0...-1....1...-1....0....0....0....0...-1...-1...-1...-1....0....1....1
..1...-1...-1....1....1...-1....1....1...-1....0...-1....0...-1....1...-1....1
..1....0...-1....0...-1....1....1...-1....1....1....1...-1....1...-1....0....1
..0...-1...-1...-1....1...-1...-1....0....1...-1....0...-1....0....1....1...-1
..1....1....0....1....1...-1....0...-1....0....0....1....0...-1...-1....0....0
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|