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A058870 Number of 2-trees 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 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

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Last modified November 21 11:01 EST 2018. Contains 317447 sequences. (Running on oeis4.)