A203289 Number of arrays of 2n nondecreasing integers in -6..6 with sum zero and equal numbers greater than zero and less than zero

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

R. H. Hardin, Table of n, a(n) for n = 1..121

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

Adjacent sequences: A203286 A203287 A203288 * A203290 A203291 A203292

Keyword

nonn

Author

R. H. Hardin Dec 31 2011

Status

approved