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

1,3

References

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

Links

Table of n, a(n) for n=1..23.

Formula

H. and P. give g.f.

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).

Sequence in context: A017958 A017959 A100069 * A219436 A219137 A240342

Adjacent sequences: A058867 A058868 A058869 * A058871 A058872 A058873

Keyword

nonn,easy

Author

N. J. A. Sloane, Jan 06 2001

Extensions

More terms from Vladeta Jovovic, Aug 22 2001

Status

approved