A211529 Number of -1..1 arrays x(i) of n+1 elements i=1..n+1 with set{t,u,v in 0,1}((x[i+t]+x[j+u]+x[k+v])*(-1)^(t+u+v)) having two, four, five or six distinct values for every i,j,k<=n.

8, 22, 42, 80, 140, 254, 448, 820, 1490, 2788, 5220, 9974, 19112, 37100, 72226, 141724, 278732, 550774, 1090128, 2163668, 4299314, 8557076, 17044564, 33984118, 67793624, 135319900, 270197826, 539710892, 1078295036, 2154827702, 4306766272

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..63

Formula

Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 9*a(n-3) + 10*a(n-4) + 2*a(n-5) - 4*a(n-6).

Empirical g.f.: 2*x*(4 - 5*x - 15*x^2 + 14*x^3 + 11*x^4 - 2*x^5) / ((1 - x)*(1 - 2*x)*(1 - x - x^2)*(1 - 2*x^2)). - Colin Barker, Jul 18 2018

Example

Some solutions for n=5:
.-1....0....1...-1...-1....1....0...-1....1...-1...-1...-1...-1....0....1....0
.-1...-1....1...-1....1....1...-1....1...-1....1....0...-1....1...-1...-1....1
.-1....0...-1....0....1....1...-1...-1....1...-1....1...-1....0....0....1....1
.-1...-1....1...-1....1....1....0....0...-1...-1....0....1....1....1....1....1
..1...-1....1....0...-1....1...-1...-1...-1....1....1....1....0....0...-1....0
..1....0...-1...-1....1....0....0....0....1...-1....0....1....1....1....1....1

Crossrefs

Sequence in context: A113744 A058508 A134783 * A069099 A172473 A145067

Adjacent sequences: A211526 A211527 A211528 * A211530 A211531 A211532

Keyword

nonn

Author

R. H. Hardin, Apr 14 2012

Status

approved