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 A259881 #12 Jun 26 2017 23:02:04 %S A259881 1,1,1,1,1,2,2,4,4,6,6,8,10,14,28,24,29,36,44 %N A259881 Erroneous version of A005186. %H A259881 S. N. Anderson, <a href="http://www.jstor.org/stable/3617045">Struggling with the 3x+1 problem</a>, Math. Gazette, 71 (1987), 271-274. %H A259881 S. N. Anderson, <a href="/A005186/a005186_1.pdf">Struggling with the 3x+1 problem</a>, Math. Gazette, 71 (1987), 271-274. [Annotated scanned copy] %H A259881 R. K. Guy, S. N. Anderson, and N. J. A. Sloane, <a href="/A005186/a005186.pdf">Correspondence</a>, 1988. %K A259881 dead %O A259881 0,6