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A250230
Number of length 3+1 0..n arrays with the sum of the cubes of adjacent differences multiplied by some arrangement of +-1 equal to zero.
1
8, 27, 52, 89, 132, 187, 248, 321, 400, 491, 588, 697, 812, 939, 1072, 1217, 1368, 1531, 1700, 1881, 2068, 2267, 2472, 2689, 2912, 3147, 3388, 3641, 3900, 4171, 4448, 4737, 5032, 5339, 5652, 5977, 6308, 6651, 7000, 7361, 7728, 8107, 8492, 8889, 9292, 9707
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) -2*a(n-3) +a(n-4).
Empirical for n mod 2 = 0: a(n) = (9/2)*n^2 + 4*n + 1.
Empirical for n mod 2 = 1: a(n) = (9/2)*n^2 + 4*n - (1/2).
Empirical g.f.: x*(8 + 11*x - 2*x^2 + x^3) / ((1 - x)^3*(1 + x)). - Colin Barker, Nov 12 2018
EXAMPLE
Some solutions for n=6:
..2....1....5....0....0....4....1....6....5....1....2....1....4....5....2....3
..2....4....5....4....6....4....3....3....5....4....5....3....4....5....2....2
..4....1....0....0....6....3....3....0....4....4....2....3....2....6....6....1
..6....1....5....0....0....4....1....0....3....1....2....5....0....5....2....1
CROSSREFS
Row 3 of A250229.
Sequence in context: A031295 A063144 A122013 * A250278 A223950 A339897
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 14 2014
STATUS
approved