A211461 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 or three distinct values for every i<=n and j<=n.

24, 56, 128, 254, 516, 982, 1904, 3578, 6812, 12786, 24224, 45658, 86660, 164422, 313660, 599546, 1150980, 2216138, 4281996, 8299742, 16133004, 31452126, 61458520, 120403946, 236321944, 464854866, 915752544, 1807260018, 3570943416

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-1) + 3*a(n-2) - 28*a(n-3) + 11*a(n-4) + 67*a(n-5) - 49*a(n-6) - 63*a(n-7) + 52*a(n-8) + 18*a(n-9) - 12*a(n-10).

Empirical g.f.: 2*x*(12 - 20*x - 84*x^2 + 123*x^3 + 210*x^4 - 242*x^5 - 222*x^6 + 175*x^7 + 71*x^8 - 46*x^9) / ((1 - 2*x)*(1 - x - x^2)*(1 - 2*x^2)*(1 - 3*x^2)*(1 - x - 2*x^2 + x^3)). - Colin Barker, Jul 17 2018

Example

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

Crossrefs

Sequence in context: A039375 A043198 A043978 * A208086 A232937 A190104

Adjacent sequences: A211458 A211459 A211460 * A211462 A211463 A211464

Keyword

nonn

Author

R. H. Hardin, Apr 12 2012

Status

approved