A199835 Number of -n..n arrays x(0..5) of 6 elements with zero sum and no two neighbors summing to zero.

10, 426, 3556, 15708, 49302, 124982, 273728, 538968, 978690, 1667554, 2699004, 4187380, 6270030, 9109422, 12895256, 17846576, 24213882, 32281242, 42368404, 54832908, 70072198, 88525734, 110677104, 137056136, 168241010, 204860370

Offset: 1

Author

R. H. Hardin, Nov 11 2011

Keywords

• nonn

Comments

Row 4 of A199832

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = n*(2*n+1)*(2*n-1)*(66*n^2-35*n+19)/15.

Empirical: G.f.: 2*x*(5+183*x+575*x^2+281*x^3+12*x^4) / (x-1)^6 . - R. J. Mathar, Aug 01 2014