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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 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,9

COMMENTS

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

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.

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

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Last modified April 25 18:12 EDT 2019. Contains 322461 sequences. (Running on oeis4.)