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A201874
Number of zero-sum -n..n arrays of 3 elements with first and second differences also in -n..n.
2
3, 5, 15, 21, 27, 47, 57, 67, 97, 111, 125, 165, 183, 201, 251, 273, 295, 355, 381, 407, 477, 507, 537, 617, 651, 685, 775, 813, 851, 951, 993, 1035, 1145, 1191, 1237, 1357, 1407, 1457, 1587, 1641, 1695, 1835, 1893, 1951, 2101, 2163, 2225, 2385, 2451, 2517
OFFSET
1,1
COMMENTS
Row 3 of A201873.
LINKS
FORMULA
Empirical: a(n) = a(n-1) +2*a(n-3) -2*a(n-4) -a(n-6) +a(n-7).
Empirical g.f.: x*(3 + 2*x + x^2)*(1 + 3*x^2 - 2*x^3 + x^4) / ((1 - x)^3*(1 + x + x^2)^2). - Colin Barker, Feb 15 2018
EXAMPLE
Some solutions for n=12:
.-2....8...-2...-9....2..-10....9....1....0...-5...-3....5...-6...11....3....2
..3...-4....0....1...-3....1....0....1...-3....4....0...-2....0...-1....4...-2
.-1...-4....2....8....1....9...-9...-2....3....1....3...-3....6..-10...-7....0
CROSSREFS
Sequence in context: A063185 A208854 A165260 * A059528 A070079 A142717
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 06 2011
STATUS
approved