A063687 Number of 2-trees rooted at any symmetric edge.

1, 1, 1, 2, 3, 6, 10, 21, 38, 84, 156, 352, 677, 1562, 3054, 7148, 14196, 33603, 67474, 161121, 326519, 785305, 1603111, 3878194, 7965845, 19365811, 39983300, 97610247, 202424674, 495955345, 1032460679, 2537529717, 5300256499

Offset: 0

Author

Vladeta Jovovic, Aug 22 2001

Keywords

• nonn

References

• F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 75, Eq. (3.5.9).

Crossrefs

Cf. A058870, A058866, A054581.