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A203289
Number of arrays of 2n nondecreasing integers in -6..6 with sum zero and equal numbers greater than zero and less than zero
1
7, 54, 310, 1380, 5036, 15798, 43958, 111053, 259023, 565010, 1164062, 2283094, 4289830, 7762060, 13582916, 23070101, 38147395, 61569710, 97213302, 150446614, 228597390, 341536652, 502400112, 728473703, 1042269641, 1472826974
OFFSET
1,1
COMMENTS
Column 6 of A203291
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) -4*a(n-2) -2*a(n-3) +4*a(n-4) -3*a(n-5) +7*a(n-6) -4*a(n-7) -4*a(n-9) -4*a(n-10) +9*a(n-11) +2*a(n-13) -2*a(n-14) -9*a(n-16) +4*a(n-17) +4*a(n-18) +4*a(n-20) -7*a(n-21) +3*a(n-22) -4*a(n-23) +2*a(n-24) +4*a(n-25) -4*a(n-26) +a(n-27)
EXAMPLE
Some solutions for n=3
.-5...-6...-3...-3...-2...-5...-4...-5...-6...-3...-4...-4...-6...-2...-3...-6
.-5...-2...-3...-3...-2...-4...-4...-4...-6...-3...-4...-4...-4...-2...-2...-5
.-2...-1....0...-1...-2...-3...-3...-3...-2...-2...-2...-1...-4....0...-2...-4
..1....1....0....1....1....1....1....3....4....1....2....1....3....0....1....5
..5....2....2....1....1....5....5....3....5....2....2....3....5....2....2....5
..6....6....4....5....4....6....5....6....5....5....6....5....6....2....4....5
CROSSREFS
Sequence in context: A194929 A317689 A116202 * A204258 A081008 A116472
KEYWORD
nonn
AUTHOR
R. H. Hardin Dec 31 2011
STATUS
approved