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A183920 Number of nondecreasing arrangements of n numbers in -2..2 with sum zero and sum of squares not greater than n*6/3. 1
1, 2, 4, 6, 9, 13, 17, 24, 31, 38, 49, 61, 72, 88, 105, 122, 144, 167, 190, 220, 250, 280, 318, 357, 395, 442, 490, 538, 595, 653, 711, 780, 849, 918, 999, 1081, 1162, 1256, 1351, 1446, 1554, 1663, 1772, 1896, 2020, 2144, 2284, 2425, 2565, 2722, 2880, 3038, 3213 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A183927.

LINKS

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

FORMULA

Empirical: a(n) = a(n-1)+2*a(n-3)-a(n-4)-a(n-5)-a(n-6)-a(n-7)+2*a(n-8)+a(n-10)-a(n-11).

Empirical g.f.: x*(1 + x + 2*x^2 - x^5 - x^6 + 2*x^7 + x^9 - x^10) / ((1 - x)^4*(1 + x)*(1 + x^2)*(1 + x + x^2)^2). - Colin Barker, Oct 21 2017

EXAMPLE

All solutions for n=4

.-1....0...-1...-2...-1...-2

.-1....0....0....0...-1....0

..0....0....0....1....1....0

..2....0....1....1....1....2

CROSSREFS

Sequence in context: A232739 A006697 A294860 * A079717 A247179 A319158

Adjacent sequences:  A183917 A183918 A183919 * A183921 A183922 A183923

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 08 2011

STATUS

approved

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Last modified March 26 20:42 EDT 2019. Contains 321534 sequences. (Running on oeis4.)