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A229016
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Number of arrays of median of three adjacent elements of some length 8 0..n array, with no adjacent equal elements in the latter.
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1
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2, 105, 830, 3527, 10860, 27379, 60180, 119653, 220318, 381749, 629586, 996635, 1524056, 2262639, 3274168, 4632873, 6426970, 8760289, 11753990, 15548367, 20304740, 26207435, 33465852, 42316621, 53025846, 65891437, 81245530, 99456995
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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) = (11/90)*n^6 + (11/5)*n^5 + (167/36)*n^4 - (43/6)*n^3 + (583/180)*n^2 - (61/30)*n + 1.
G.f.: x*(2 + 91*x + 137*x^2 - 148*x^3 - 4*x^4 + 9*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=4:
..3....2....3....1....1....0....1....1....1....0....2....4....3....1....1....1
..3....2....3....3....1....1....1....0....2....1....4....2....0....3....2....1
..4....0....2....3....1....3....3....3....2....2....2....2....4....3....2....0
..1....4....3....3....1....3....0....3....2....2....4....1....2....3....1....1
..3....0....3....4....0....4....3....3....2....4....1....2....2....1....0....0
..0....1....3....0....2....2....3....1....0....3....3....1....1....3....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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