A199709 Number of -n..n arrays x(0..6) of 7 elements with zero sum and no two neighbors equal.

56, 2642, 27854, 149942, 559028, 1643204, 4099204, 9059092, 18251656, 34171380, 60292468, 101279218, 163252890, 254042820, 383508158, 563826638, 809873706, 1139548482, 1574209250, 2139036592, 2863528108, 3781894246, 4933615190

Offset: 1

Author

R. H. Hardin Nov 09 2011

Keywords

• nonn

Comments

Row 7 of A199704

Examples

			Some solutions for n=5
.-4....2...-5....0...-4...-4...-5....0....1....1....0...-5....2...-5....1....2
..1...-5....2....2....1....2....1...-5....0...-5...-4....0...-5....0...-4....1
..5....3...-1...-2....4...-1....4...-3....3....1....4....4...-4....3...-3....2
..4....4....5....4...-4....3....2....1...-1....3...-1...-5....4....1....2...-1
.-1....3...-3....2....4...-1....5....2...-2...-2...-2...-1....2....3....5...-5
.-4...-4...-2...-5....1....2...-5....1....3...-1....5....4...-1...-2....0...-1
.-1...-3....4...-1...-2...-1...-2....4...-4....3...-2....3....2....0...-1....2
		

Links

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

Formula

Empirical: a(n)=2*a(n-1)-a(n-3)-a(n-5)+a(n-6)-2*a(n-7)+2*a(n-8)+a(n-9)-a(n-13)-2*a(n-14)+2*a(n-15)-a(n-16)+a(n-17)+a(n-19)-2*a(n-21)+a(n-22)