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 A153831 #4 Mar 31 2012 14:02:29 %S A153831 68,73,74,83,84,87,88,183,184,189,190,199,202,203,252,254,261,262,268, %T A153831 269,270,271,515,537,539,573,575,591,593,871,894,895,990,995,996,1110, %U A153831 1132,1134,1466,1489,1490,1585,1590,1591,1600,1601,1604,1605,2213 %N A153831 Index sequence to A089840: set-wise difference of A153829 and A153830. %C A153831 The terms give the positions to bijections in A089840 which preserve A153835/A127302 (the non-oriented form of binary trees), but do not extend uniquely to automorphisms of an infinite binary tree. %H A153831 A. Karttunen, <a href="/A153831/b153831.txt">Table of n, a(n) for n = 0..2933</a> %H A153831 A. Karttunen, <a href="/A089839/a089839.c.txt">C-program for computing the initial terms of this sequence</a> %Y A153831 Cf. also A153826, A153827, A153828, A153832, A153833. %K A153831 nonn %O A153831 0,1 %A A153831 _Antti Karttunen_, Jan 07 2009