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A250338
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Number of length 2+5 0..n arrays with every six consecutive terms having the maximum of some three terms equal to the minimum of the remaining three terms.
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1
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68, 907, 5264, 20085, 59396, 147903, 325312, 651369, 1211620, 2123891, 3545488, 5681117, 8791524, 13202855, 19316736, 27621073, 38701572, 53253979, 72097040, 96186181, 126627908, 164694927, 211841984, 269722425, 340205476, 425394243
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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^6 + 9*n^5 + 20*n^4 + (68/3)*n^3 + 12*n^2 + (7/3)*n + 1.
G.f.: x*(68 + 431*x + 343*x^2 - 96*x^3 - 20*x^4 - 7*x^5 + x^6) / (1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.
(End)
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EXAMPLE
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Some solutions for n=6:
..2....0....3....0....4....4....3....3....0....2....2....2....3....0....0....3
..1....0....4....6....5....0....5....5....2....2....2....2....4....5....0....5
..3....2....5....2....5....2....6....2....2....0....1....4....3....5....6....3
..3....2....6....3....5....2....6....0....3....1....2....3....4....2....0....5
..4....5....4....2....3....2....3....2....4....5....5....3....6....2....0....5
..3....6....1....0....5....4....5....2....2....2....1....3....6....0....0....5
..5....1....4....2....0....4....0....0....1....5....5....6....1....2....4....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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