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 A121264 #9 Jul 06 2018 04:46:43 %S A121264 2,3,5,26,1370,9840770,851566070376026 %N A121264 See Comments for definition. %C A121264 We use N_b to denote "N read in base b". Similar to A121263, but now we write the numerals in the stack in binary: %C A121264 ......10....10.....10......10........etc. %C A121264 ..............11.....11......11.......... %C A121264 .......................100.....100....... %C A121264 ..................................101.... %C A121264 The next two terms have about 144 and 450 digits respectively. %C A121264 A "dungeon" of numbers. %D A121264 David Applegate, Marc LeBrun and N. J. A. Sloane, Descending Dungeons and Iterated Base-Changing, in "The Mathematics of Preference, Choice and Order: Essays in Honor of Peter Fishburn", edited by Steven Brams, William V. Gehrlein and Fred S. Roberts, Springer, 2009, pp. 393-402. %H A121264 David Applegate, Marc LeBrun and N. J. A. Sloane, <a href="https://arxiv.org/abs/math/0611293">Descending Dungeons and Iterated Base-Changing</a>, arXiv:math/0611293 [math.NT], 2006-2007. %H A121264 David Applegate, Marc LeBrun, N. J. A. Sloane, <a href="https://www.jstor.org/stable/40391135">Descending Dungeons, Problem 11286</a>, Amer. Math. Monthly, 116 (2009) 466-467. %Y A121264 Cf. A121263, A121265. %K A121264 nonn,base %O A121264 1,1 %A A121264 _Marc LeBrun_, Aug 23 2006