A211465 Number of -2..2 arrays x(i) of n+1 elements i=1..n+1 with x(i)+x(j), x(i+1)+x(j+1), -(x(i)+x(j+1)), and -(x(i+1)+x(j)) having two, three or four distinct values for every i<=n and j<=n.

24, 116, 556, 2652, 12588, 59484, 279932, 1312364, 6131052, 28550492, 132555868, 613748556, 2834515596, 13060107900, 60044009084, 275496757868, 1261682707500, 5768039837468, 26327131807900, 119984300243340, 546053643671244

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 12*a(n-1) - 45*a(n-2) + 40*a(n-3) + 46*a(n-4) + 8*a(n-5).

Empirical g.f.: 4*x*(6 - 43*x + 61*x^2 + 60*x^3 + 10*x^4) / ((1 - 4*x)*(1 - 4*x - x^2)*(1 - 4*x - 2*x^2)). - Colin Barker, Jul 18 2018

Example

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

Crossrefs

Sequence in context: A126411 A211580 A211594 * A371184 A371160 A371200

Adjacent sequences: A211462 A211463 A211464 * A211466 A211467 A211468

Keyword

nonn

Author

R. H. Hardin, Apr 12 2012

Status

approved