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 A121297 #9 Nov 19 2017 12:59:15 %S A121297 11,14,21,39,78,211,1954,63163,17163259,316235916142, %T A121297 7475840758734855197,77068358083998565749275388634420, %U A121297 56080446471298599543571746837309517827424625680076701163 %N A121297 For definition see Comments lines. %C A121297 Using N_b to denote "N read in base b", the sequence is %C A121297 ......11....11.....11.....11.......etc. %C A121297 ..............13.....13.....13......... %C A121297 .......................17.....17....... %C A121297 ................................19..... %C A121297 where the subscripts are evaluated from the top downwards. %C A121297 Analog of A121265 using primes >= 11. %D A121297 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 A121297 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 A121297 David Applegate, Marc LeBrun and N. J. A. Sloane, <a href="https://www.jstor.org/stable/40391135">Descending Dungeons, Problem 11286</a>, Amer. Math. Monthly, 116 (2009) 466-467. %p A121297 asubb := proc(a,b) local t1; t1:=convert(a,base,10); add(t1[j]*b^(j-1),j=1..nops(t1)): end; %p A121297 t1:=[10]; for n from 1 to 12 do t2:=f(t1[n],ithprime(n+5)); t1:=[op(t1),t2]; od: t1; %Y A121297 Cf. A121263, A121265, A121295, A121296. %K A121297 nonn,base %O A121297 10,1 %A A121297 _N. J. A. Sloane_, Aug 25 2006