A058866 Number of 2-trees rooted at an edge.

1, 2, 6, 21, 83, 356, 1599, 7434, 35381, 171508, 843419, 4197179, 21094355, 106915928, 545859112, 2804656069, 14491370996, 75248398034, 392476363133, 2055245992376, 10801442696736, 56953957110855, 301207378815752

Offset

1,2

References

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 75, Eq. (3.5.11).

Links

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

Formula

H. and P. give g.f.

Crossrefs

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).

Cf. A058870, A054581.

Sequence in context: A329055 A148495 A150221 * A063689 A178325 A087649

Adjacent sequences: A058863 A058864 A058865 * A058867 A058868 A058869

Keyword

nonn,easy

Author

N. J. A. Sloane, Jan 06 2001

Extensions

More terms from Vladeta Jovovic, Aug 22 2001

Status

approved