A101204 Triangle read by rows: T(n,k) = number of planar trivalent (or cubic) loopless multigraphs with 2n nodes and exactly k double bonds, for 0 <= k <= n.
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
Offset: 0
Examples
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, ...
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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