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A188182
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Number of strictly increasing arrangements of 4 numbers in -(n+2)..(n+2) with sum zero
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1
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5, 12, 24, 43, 69, 104, 150, 207, 277, 362, 462, 579, 715, 870, 1046, 1245, 1467, 1714, 1988, 2289, 2619, 2980, 3372, 3797, 4257, 4752, 5284, 5855, 6465, 7116, 7810, 8547, 9329, 10158, 11034, 11959, 12935, 13962, 15042, 16177, 17367, 18614, 19920, 21285
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n)=3*a(n-1)-3*a(n-2)+2*a(n-3)-3*a(n-4)+3*a(n-5)-a(n-6).
Empirical: a(n) = (n+1)*(4*n^2+17*n+22)/18 -2 *A049347(n)/9; g.f. -x*(-5+3*x-3*x^2+3*x^3-3*x^4+x^5) / ( (1+x+x^2)*(x-1)^4 ). - R. J. Mathar, Mar 26 2011
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EXAMPLE
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Some solutions for n=5
.-6...-7...-6...-5...-3...-7...-4...-5...-4...-5...-6...-2...-6...-6...-7...-4
.-4....0...-1...-4....0...-1...-3...-3...-2...-2...-5...-1...-3...-3....0...-3
..3....1....3....4....1....2....0....1....2....2....5....0....3....2....3....1
..7....6....4....5....2....6....7....7....4....5....6....3....6....7....4....6
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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