

A101204


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.


2



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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OFFSET

0,9


COMMENTS

The entries in the first two rows are "by convention".


REFERENCES

A. T. Balaban, Enumeration of Cyclic Graphs, pp. 63105 of A. T. Balaban, ed., Chemical Applications of Graph Theory, Ac. Press, 1976; see p. 92.


LINKS

Table of n, a(n) for n=0..28.


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 ...


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: A232095 A279436 A082470 * A169808 A283069 A304528
Adjacent sequences: A101201 A101202 A101203 * A101205 A101206 A101207


KEYWORD

nonn,tabl


AUTHOR

N. J. A. Sloane, Dec 13 2004


STATUS

approved



