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A292207
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Number of unrooted unlabelled bipartite cubic maps on a compact closed oriented surface with 2*n vertices (and thus 3*n edges).
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0
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2, 3, 16, 133, 1440, 22076, 401200, 8523946, 206375088, 5611089408, 169259764912, 5610386295418, 202710195084400, 7929759557219228, 333909047017798272, 15059194651009154172, 724232293050284717248
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OFFSET
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0,1
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COMMENTS
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Equivalently, the number of unrooted bicolored triangulations with 2*n triangles (and thus 3*n edges).
Equivalently, the number of pairs of permutations (alpha,sigma) up to simultaneous conjugacy on a set of size 3*n with alpha^3=sigma^3=1, acting transitively and without fixed points.
There is no recurrence relation known for this sequence.
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LINKS
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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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