A211528 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 or six distinct values for every i,j,k<=n.

8, 18, 34, 64, 116, 214, 392, 732, 1370, 2604, 4972, 9598, 18608, 36340, 71210, 140196, 276692, 547710, 1086040, 2157532, 4291130, 8544796, 17028188, 33959550, 67760864, 135270756, 270132298, 539612596, 1078163972, 2154631102, 4306504136

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..69

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 - 7*x - 11*x^2 + 18*x^3 + 5*x^4 - 6*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...-1....1...-1...-1....1....0...-1...-1....0...-1....1....1...-1....0...-1
..1...-1....0....1...-1...-1....1...-1...-1....1....1....1....1...-1...-1...-1
.-1....0....1....1...-1...-1....1....1....0....0...-1....1....1...-1...-1....1
..1...-1....0....1....1...-1....0...-1...-1....1...-1...-1....1...-1...-1....1
..1....0....1....1....1....1....1...-1...-1....1....1....1....1...-1...-1...-1
.-1...-1....0....1...-1...-1....1...-1....0....1....1....1....0....0....0...-1

Crossrefs

Sequence in context: A171523 A120091 A211526 * A297841 A098944 A129958

Adjacent sequences: A211525 A211526 A211527 * A211529 A211530 A211531

Keyword

nonn

Author

R. H. Hardin, Apr 14 2012

Status

approved