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A201813 Number of arrays of 5 integers in -n..n with sum zero and equal numbers of elements greater than zero and less than zero. 1
51, 221, 631, 1401, 2651, 4501, 7071, 10481, 14851, 20301, 26951, 34921, 44331, 55301, 67951, 82401, 98771, 117181, 137751, 160601, 185851, 213621, 244031, 277201, 313251, 352301, 394471, 439881, 488651, 540901, 596751, 656321, 719731 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 5 of A201811.

LINKS

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

FORMULA

Empirical: a(n) = 20*n^3 + 30*n + 1.

Conjectures from Colin Barker, May 25 2018: (Start)

G.f.: x*(51 + 17*x + 53*x^2 - x^3) / (1 - x)^4.

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.

(End)

EXAMPLE

Some solutions for n=17.

..6...13...-8...15..-12...-6...15....0..-13...-5...16....0...17...-4...-3...11

..0...-2....9....3...-2....0..-12....3....0..-17..-17..-16....5....0....0...-8

.-8..-12....7...-8....0....6...13...13..-11...12....0...-7...-5...13....7....0

..6....0...-8..-10....1...-3..-16..-10....8...10....3....8..-17..-16....1....2

.-4....1....0....0...13....3....0...-6...16....0...-2...15....0....7...-5...-5

CROSSREFS

Cf. A201811.

Sequence in context: A158640 A107253 A030535 * A193250 A204717 A253921

Adjacent sequences:  A201810 A201811 A201812 * A201814 A201815 A201816

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 05 2011

STATUS

approved

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Last modified October 18 07:19 EDT 2019. Contains 328146 sequences. (Running on oeis4.)