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A188334 Number of nondecreasing arrangements of 4 nonzero numbers in -(n+2)..(n+2) with sum zero 1
10, 20, 37, 61, 94, 136, 191, 257, 338, 434, 547, 677, 828, 998, 1191, 1407, 1648, 1914, 2209, 2531, 2884, 3268, 3685, 4135, 4622, 5144, 5705, 6305, 6946, 7628, 8355, 9125, 9942, 10806, 11719, 12681, 13696, 14762, 15883, 17059, 18292, 19582, 20933, 22343 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A188333

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n)=2*a(n-1)-a(n-3)-a(n-4)+2*a(n-6)-a(n-7).

Empirical: -x*(-10+3*x^2+3*x^3-2*x^4-5*x^5+3*x^6) / ( (1+x)*(1+x+x^2)*(x-1)^4 ). a(n) = n^5/15-5*n^4/6+35*n^3/9-5*n^2 +253*n/30 +29/9 -2*A049347(n)/9. - R. J. Mathar, Mar 28 2011

EXAMPLE

Some solutions for n=6

.-6...-7...-6...-8...-4...-2...-5...-8...-6...-5...-5...-4...-6...-4...-8...-4

..1...-5...-1...-5...-3...-2...-5....1...-6....1...-2...-4...-3...-3...-3...-3

..2....5...-1....6....2...-1....4....2....6....1...-1....4....4....3....4....1

..3....7....8....7....5....5....6....5....6....3....8....4....5....4....7....6

CROSSREFS

Sequence in context: A046285 A048030 A048011 * A266087 A047881 A172172

Adjacent sequences:  A188331 A188332 A188333 * A188335 A188336 A188337

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 28 2011

STATUS

approved

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Last modified November 21 17:44 EST 2017. Contains 295004 sequences.