A203290 Number of arrays of 2n nondecreasing integers in -7..7 with sum zero and equal numbers greater than zero and less than zero.

8, 80, 580, 3172, 13934, 51768, 168314, 491187, 1310474, 3241912, 7518232, 16487840, 34435060, 68887342, 132636714, 246789735, 445262312, 781274626, 1336560456, 2234216814, 3656356722, 5868037410, 9249277184, 14337411833

Offset: 1

Author

R. H. Hardin Dec 31 2011

Keywords

• nonn

Comments

Column 7 of A203291

Examples

			Some solutions for n=3
.-6...-5...-7...-7...-6...-7...-6...-7...-7...-6...-7...-7...-7...-7...-5...-7
.-4...-4...-7...-6...-1...-5...-6...-3...-6...-2...-6...-4...-2...-4...-5...-2
..0...-2...-1...-1...-1...-5...-3...-1...-3...-2...-2...-1...-1...-1...-3...-2
..0....1....5....4....1....5....3....3....3....2....4....1....3....3....4....3
..5....3....5....4....1....5....6....3....6....4....5....4....3....4....4....3
..5....7....5....6....6....7....6....5....7....4....6....7....4....5....5....5
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..97

Formula

Empirical: a(n) = 4*a(n-1) -4*a(n-2) -2*a(n-3) +4*a(n-4) -2*a(n-5) +4*a(n-6) -4*a(n-7) +6*a(n-8) -6*a(n-9) -5*a(n-10) +4*a(n-11) +a(n-12) +2*a(n-13) +12*a(n-15) -17*a(n-16) +2*a(n-17) -2*a(n-18) +2*a(n-20) -2*a(n-21) +17*a(n-22) -12*a(n-23) -2*a(n-25) -a(n-26) -4*a(n-27) +5*a(n-28) +6*a(n-29) -6*a(n-30) +4*a(n-31) -4*a(n-32) +2*a(n-33) -4*a(n-34) +2*a(n-35) +4*a(n-36) -4*a(n-37) +a(n-38)