This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A058870 #6 May 10 2013 12:44:33 %S A058870 0,1,4,18,77,346,1578,7396,35297,171352,843067,4196502,21092793, %T A058870 106912874,545851964,2804641873,14491337393,75248330560,392476202012, %U A058870 2055245665857,10801441911431,56953955507744,301207374937558 %N A058870 Number of 2-trees rooted at an asymmetric edge. %D A058870 F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 75, Eq. (3.5.10). %F A058870 H. and P. give g.f. %Y A058870 Cf. A058870, A058866, A054581. %Y A058870 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). %K A058870 nonn,easy %O A058870 1,3 %A A058870 _N. J. A. Sloane_, Jan 06 2001 %E A058870 More terms from _Vladeta Jovovic_, Aug 22 2001