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A357242
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Number of n node tournaments that have exactly two circular triads.
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3
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24, 240, 2240, 21840, 228480, 2580480, 31449600, 412473600, 5801241600, 87178291200, 1394852659200, 23683435776000, 425430061056000, 8062248370176000, 160770717499392000, 3365514444644352000, 73798027581358080000, 1691677863018823680000, 40464026199993876480000
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OFFSET
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4,1
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LINKS
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FORMULA
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a(n) = n!*(n - 3 + (1/18)*(n - 4)*(n - 5)) (proven by Kadane).
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EXAMPLE
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For n = 4 the a(4) = 24 solution is 4!*(4 - 3 + (1/18)*(4 - 4)*(4 - 5)) = 24.
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PROG
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(R) fact(n)*(n-3+(1/18)*(n-4)*(n-5))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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