A211567 Number of -2..2 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 or four distinct values for every i,j,k<=n.

24, 40, 68, 122, 220, 410, 764, 1454, 2764, 5330, 10268, 19982, 38860, 76130, 149084, 293534, 577804, 1141970, 2256668, 4472942, 8865100, 17610050, 34979804, 69601214, 138485644, 275900210, 549658268, 1096111502, 2185812940, 4362027170

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..73

Formula

Empirical: a(n) = 3*a(n-1) + 3*a(n-2) - 15*a(n-3) + 4*a(n-4) + 18*a(n-5) - 12*a(n-6).

Empirical g.f.: 2*x*(12 - 16*x - 62*x^2 + 79*x^3 + 77*x^4 - 94*x^5) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)*(1 - 3*x^2)). - Colin Barker, Jul 19 2018

Example

Some solutions for n=5:
..2...-2...-1....2...-2....1....0....0....0....0....1....1...-2....2....0...-1
..1...-2....1....2....1...-1...-2...-1....1....1....0....2...-1....0....2...-1
..0....2....1...-2...-2....1....0...-2....2....0....1....1....0...-2....0...-1
..1....2...-1...-2....1....1...-2...-1....1...-1....0....2...-1....0...-2....1
..2....2...-1...-2...-2....1....0....0....0....0...-1....1....0....2....0....1
..1...-2...-1...-2....1....1...-2...-1....1...-1...-2....2...-1....0....2....1

Crossrefs

Sequence in context: A195562 A026040 A259217 * A316271 A357699 A328375

Adjacent sequences: A211564 A211565 A211566 * A211568 A211569 A211570

Keyword

nonn

Author

R. H. Hardin, Apr 16 2012

Status

approved