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A166756
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Number of nX2 1..3 arrays containing at least one of each value, and all equal values connected.
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1
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0, 24, 174, 642, 1716, 3780, 7314, 12894, 21192, 32976, 49110, 70554, 98364, 133692, 177786, 231990, 297744, 376584, 470142, 580146, 708420, 856884, 1027554, 1222542, 1444056, 1694400, 1975974, 2291274, 2642892, 3033516, 3465930, 3943014, 4467744
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OFFSET
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1,2
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LINKS
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FORMULA
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Empirical: a(n) = 4*n^4 - 8*n^3 + 11*n^2 - 13*n + 6.
Empirical G.f.: 6*x^2*(x^3 + 2*x^2 + 9*x + 4)/(1 - x)^5.
Empirical E.g.f.: (6 - 6*x + 15*x^2 + 16*x^3 + 4*x^4)*exp(x) - 6. (End)
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EXAMPLE
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Some solutions for n=4
...1.1...2.3...1.1...3.2...3.3...2.2...2.2...3.1...2.3...2.3...2.1...3.3...1.1
...1.3...2.1...3.1...2.2...3.1...1.2...2.1...2.1...2.2...2.3...2.1...3.2...2.1
...1.2...2.2...2.1...1.1...3.1...1.1...2.3...1.1...2.1...2.3...1.1...3.1...3.3
...2.2...2.2...1.1...1.1...2.1...3.3...3.3...1.1...1.1...1.1...3.3...1.1...3.3
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...3.3...1.3...1.2...1.2...3.3...3.1...3.2...3.3...2.1...3.2...1.1...2.2...1.1
...3.1...1.1...1.2...1.3...3.3...3.3...3.3...3.2...1.1...3.3...1.3...2.1...2.2
...1.1...1.2...1.1...3.3...1.1...3.3...3.3...2.2...3.1...3.3...1.1...2.2...2.2
...2.1...2.2...3.1...3.3...2.1...2.2...1.1...2.1...1.1...1.3...2.2...3.2...2.3
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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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