A211721 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 two or four distinct values for every i,j,k<=n.

48, 74, 120, 210, 376, 700, 1312, 2508, 4800, 9288, 17968, 35000, 68144, 133312, 260688, 511616, 1003728, 1974896, 3884688, 7659696, 15100048, 29828560, 58914064, 116565456, 230605584, 456911760, 905224720, 1795793552, 3562275344

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..64

Formula

Empirical: a(n) = 3*a(n-1) + 4*a(n-2) - 18*a(n-3) + 2*a(n-4) + 30*a(n-5) - 16*a(n-6) - 12*a(n-7) + 8*a(n-8).

Empirical g.f.: 2*x*(24 - 35*x - 147*x^2 + 209*x^3 + 251*x^4 - 348*x^5 - 102*x^6 + 140*x^7) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)*(1 - 4*x^2 + 2*x^4)). - Colin Barker, Jul 20 2018

Example

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

Crossrefs

Sequence in context: A033821 A334899 A165039 * A057533 A005276 A328370

Adjacent sequences: A211718 A211719 A211720 * A211722 A211723 A211724

Keyword

nonn

Author

R. H. Hardin, Apr 20 2012

Status

approved