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A101204
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Triangle read by rows: T(n,k) = number of planar trivalent (or cubic) multigraphs with 2n nodes and exactly k double bonds, for 0 <= k <= n.
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2
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1, 0, 1, 1, 0, 1, 1, 1, 2, 1, 3, 4, 5, 4, 1, 9, 16, 22, 16, 7, 1, 32, 75, 112, 86, 41, 10, 1, 133
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 0,9
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COMMENTS
| The entries in the first two rows are "by convention".
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REFERENCES
| A. T. Balaban, Enumeration of Cyclic Graphs, pp. 63-105 of A. T. Balaban, ed., Chemical Applications of Graph Theory, Ac. Press, 1976; see p. 92.
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EXAMPLE
| Triangle begins
1
0 1
1 0 1
1 1 2 1
3 4 5 4 1
9 16 22 16 7 1
32 75 112 86 41 10 1
133 ...
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CROSSREFS
| Row sums give A005966. First column is A005964 (trivalent connected planar graphs with 2n nodes). Second and third columns give A101205, A101206.
Sequence in context: A088267 A117407 A082470 * A169808 A175499 A181440
Adjacent sequences: A101201 A101202 A101203 * A101205 A101206 A101207
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KEYWORD
| nonn,tabl
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Dec 13 2004
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