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A247727
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Number of length 1+3 0..n arrays with no disjoint pairs in any consecutive four terms having the same sum.
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1
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8, 48, 168, 440, 960, 1848, 3248, 5328, 8280, 12320, 17688, 24648, 33488, 44520, 58080, 74528, 94248, 117648, 145160, 177240, 214368, 257048, 305808, 361200, 423800, 494208, 573048, 660968, 758640, 866760, 986048, 1117248, 1261128
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = n^4 + 2*n^3 + 3*n^2 + 2*n.
G.f.: 8*x*(1 + x + x^2) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.
(End)
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EXAMPLE
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Some solutions for n=6:
..0....4....1....2....0....1....4....0....4....0....3....0....0....0....3....2
..1....4....0....5....6....5....6....3....1....5....6....3....5....2....0....5
..2....2....1....3....5....1....4....6....0....1....6....3....5....0....1....2
..5....3....5....3....3....0....3....5....2....5....2....4....5....0....1....4
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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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