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A188182 Number of strictly increasing arrangements of 4 numbers in -(n+2)..(n+2) with sum zero 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A188181

LINKS

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

FORMULA

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

EXAMPLE

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

CROSSREFS

Sequence in context: A018806 A101425 A191831 * A187210 A126880 A108314

Adjacent sequences:  A188179 A188180 A188181 * A188183 A188184 A188185

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 23 2011

STATUS

approved

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Last modified August 20 03:34 EDT 2017. Contains 290823 sequences.