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A007100
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Number of labeled trivalent (or cubic) 3-connected graphs with 2n nodes.
(Formerly M5343)
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2
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1, 70, 16800, 9238320, 9520156800, 16305064776000, 42856575521760000, 163329351308323200000, 864876880105205071104000, 6155146233167046820024320000, 57316399761348433188962519040000
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listen;
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OFFSET
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2,2
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REFERENCES
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R. W. Robinson, personal communication.
R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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a(n) = (2*n)!*r(n)/(3*n*2^n) where r(2) = 1 and r(n) = (3*n-2) * (r(n-1) + Sum_{i=2..n-2} r(i) * r(n-i)). - Sean A. Irvine, Oct 11 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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STATUS
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approved
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