A201807 Number of arrays of n integers in -4..4 with sum zero and equal numbers of elements greater than zero and less than zero.

1, 9, 25, 313, 1401, 15681, 90609, 909945, 6105913, 57290209, 421304049, 3799765201, 29595440785, 261111392985, 2109792275145, 18400232046585, 152275971653625, 1320864136716225, 11107129707193809, 96160509723165393, 817518139811725713, 7077960886109335737, 60642227399014653225

Offset: 1

Author

R. H. Hardin, Dec 05 2011

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 4 of A201811.