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A201806
Number of arrays of n integers in -3..3 with sum zero and equal numbers of elements greater than zero and less than zero.
1
1, 7, 19, 151, 631, 4621, 23857, 164599, 948871, 6359617, 38944357, 258107389, 1636264813, 10819063087, 70033892299, 463844386999, 3042796871863, 20218887555601, 133836585431269, 892623030133681, 5947033694372881
OFFSET
1,2
LINKS
EXAMPLE
Some solutions for n=7:
.-3....2....0...-1...-3....3....1....3...-1....3....0...-2....1...-3....0...-3
.-3....3...-2...-1....1....1...-1....2...-3....3....1....3....3...-2....0....3
.-3....0....3...-2...-1....0...-2...-2....1....1...-2...-3....0....1....2....0
..3...-3...-2....2...-1...-1....3...-2....2...-2....2....3....2....0...-3....0
..3....2....3....1....3....1....0....0....0...-2...-2....2...-1....3...-2....0
..3...-3....1....0....1...-1....1....2...-1...-3....3...-3...-3....2....0...-3
..0...-1...-3....1....0...-3...-2...-3....2....0...-2....0...-2...-1....3....3
CROSSREFS
Column 3 of A201811.
Sequence in context: A328713 A376907 A096321 * A346943 A128338 A173384
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 05 2011
STATUS
approved