A058866 - OEIS

%I #11 Sep 02 2022 19:17:46

%S 1,2,6,21,83,356,1599,7434,35381,171508,843419,4197179,21094355,

%T 106915928,545859112,2804656069,14491370996,75248398034,392476363133,

%U 2055245992376,10801442696736,56953957110855,301207378815752

%N Number of 2-trees rooted at an edge.

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

%F H. and P. give g.f.

%Y 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).

%Y Cf. A058870, A054581.

%K nonn,easy

%O 1,2

%A _N. J. A. Sloane_, Jan 06 2001

%E More terms from _Vladeta Jovovic_, Aug 22 2001