A211720 Number of -3..3 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 four distinct values for every i,j,k<=n.

36, 50, 72, 114, 184, 316, 544, 972, 1728, 3144, 5680, 10424, 18992, 35008, 64080, 118400, 217296, 402032, 738960, 1368240, 2517136, 4662736, 8582416, 15902160, 29278992, 54258576, 99918352, 185180816, 341049872, 632107792, 1164231696

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..60

Formula

Empirical: a(n) = a(n-1) + 6*a(n-2) - 6*a(n-3) - 10*a(n-4) + 10*a(n-5) + 4*a(n-6) - 4*a(n-7).

Empirical g.f.: 2*x*(18 + 7*x - 97*x^2 - 21*x^3 + 149*x^4 + 10*x^5 - 58*x^6) / ((1 - x)*(1 - 2*x^2)*(1 - 4*x^2 + 2*x^4)). - Colin Barker, Jul 19 2018

Example

Some solutions for n=5:
.-2....0....3....2....0...-3...-1....0....2....1...-2...-2...-2....0...-2...-3
.-1...-3....2...-1...-1...-1...-2...-3....3....0...-1...-1...-3....3...-1...-2
..0....0....1....2...-2...-3...-1....0....2...-1....0....0...-2....0...-2...-3
..1....3....0...-1...-3...-1...-2....3....1....0...-1....1...-1....3...-1...-2
..0....0....1....2...-2...-3...-1....0....2....1....0....2...-2....0....0...-1
..1...-3....0...-1...-1...-1....0....3....3....2....1....1...-3....3...-1...-2

Crossrefs

Sequence in context: A335249 A332287 A050691 * A261285 A261257 A188243

Adjacent sequences: A211717 A211718 A211719 * A211721 A211722 A211723

Keyword

nonn

Author

R. H. Hardin, Apr 20 2012

Status

approved