A200556 Number of -n..n arrays x(0..5) of 6 elements with zero sum and nonzero second differences.

72, 1240, 7254, 26850, 75792, 178834, 372150, 705270, 1242888, 2067650, 3281874, 5009232, 7397868, 10621792, 14882672, 20413220, 27478160, 36376230, 47443518, 61054528, 77624122, 97610834, 121518006, 149895400, 183343046, 222512226

Offset: 1

Author

R. H. Hardin Nov 19 2011

Keywords

• nonn

Comments

Row 4 of A200553

Examples

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

Links

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

Formula

Empirical: a(n) = a(n-1) +a(n-2) +a(n-3) -2*a(n-4) -a(n-6) -a(n-7) -a(n-8) +3*a(n-9) +3*a(n-10) -a(n-11) -a(n-12) -a(n-13) -2*a(n-15) +a(n-16) +a(n-17) +a(n-18) -a(n-19)