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A297487
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Number of maximal matchings in the complete tripartite graph K_n,n,n.
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2
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3, 14, 342, 5256, 252360, 7950960, 582346800, 30400755840, 3055726477440, 234650484230400, 30479146156166400, 3193083216360576000, 515174657767010841600, 69927761804930559129600, 13622234004598726450944000, 2307722078006148475736064000
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OFFSET
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1,1
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LINKS
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Eric Weisstein's World of Mathematics, Matching
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MATHEMATICA
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Table[3 n! HypergeometricPFQ[{(1 - n)/2, -n, -n/2}, {1}, -4] - If[Mod[n, 2] == 0, 2 (n!/(n/2)!)^3, 0], {n, 20}]
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PROG
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(PARI) a(n)={if(n%2==0, binomial(n, n/2)*(n/2)!, 0)^3 + sum(k=0, (n-1)\2, 3*binomial(n, k)^2*binomial(n, 2*k)*binomial(2*k, k)*k!^2*(n-k)!)} \\ Andrew Howroyd, Dec 30 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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