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 A006682 M3571 #20 Jul 08 2025 16:52:39
%S A006682 1,4,20,155,1716,24654,434155,9043990,217457456,5926620029,
%T A006682 180538177590,6078622845750,224156328707221,8984765008810504,
%U A006682 388939866084222200,18083736252080051435,898779656769444326136,47551736771345760732954
%N A006682 Number of binary phylogenetic trees with n labels.
%D A006682 Foulds, L. R.; Robinson, R. W. Enumeration of binary phylogenetic trees. Combinatorial mathematics, VIII (Geelong, 1980), pp. 187-202, Lecture Notes in Math., 884, Springer, Berlin-New York, 1981. Math. Rev. 83a:05071.
%D A006682 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A006682 L. R. Foulds and R. W. Robinson, <a href="/A006677/a006677.pdf">Enumeration of binary phylogenetic trees</a>, pp. 187-202, Lecture Notes in Math., 884, Springer, Berlin-New York, 1981. (Annotated scanned copy)
%H A006682 <a href="/index/Tra#trees">Index entries for sequences related to trees</a>
%F A006682 a(n) = Sum_{k=2..n} S(n, k) * A006680(k) where S(n, k) are Stirling numbers of the second kind. - _Sean A. Irvine_, Jun 16 2017
%K A006682 nonn
%O A006682 2,2
%A A006682 _N. J. A. Sloane_
%E A006682 More terms and offset corrected by _Sean A. Irvine_, Jun 16 2017