A058870 Number of 2-trees rooted at an asymmetric edge.

0, 1, 4, 18, 77, 346, 1578, 7396, 35297, 171352, 843067, 4196502, 21092793, 106912874, 545851964, 2804641873, 14491337393, 75248330560, 392476202012, 2055245665857, 10801441911431, 56953955507744, 301207374937558

Offset: 1

Author

N. J. A. Sloane, Jan 06 2001

Keywords

• nonn
• easy

References

• F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 75, Eq. (3.5.10).

Crossrefs

Cf. A058870, A058866, A054581.

Let A063687(n) be the number of 2-trees rooted at a symmetric edge (see H. and P. Eq. (3.5.9)). Then A058866(n) = A058870(n) + A063687(n).

Formula

H. and P. give g.f.

Extensions

More terms from Vladeta Jovovic, Aug 22 2001