

A058870


Number of 2trees rooted at an asymmetric edge.


8



0, 1, 4, 18, 77, 346, 1578, 7396, 35297, 171352, 843067, 4196502, 21092793, 106912874, 545851964, 2804641873, 14491337393, 75248330560, 392476202012, 2055245665857, 10801441911431, 56953955507744, 301207374937558
(list;
graph;
refs;
listen;
history;
text;
internal format)



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 2trees 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



