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 A055866 #6 Mar 30 2012 18:34:54 %S A055866 1,2,15,124,1295,117648,1073741823,109418989131512359208,0, %T A055866 9999999999999999999999999,9999999999999,999999999,9999999,999999, %U A055866 99999,99999,9999,9999,9999,9999,999,999,999,999,999,999,999,999,999 %N A055866 Largest number that has the same number of digits in base 10 and base n, or 0 if no such number exists. %C A055866 a(10)=infinity, a(22)-a(31)=999, a(32-99)=99, a(n)=9 for n >= 100. %e A055866 117648 is "666666" in base 7, larger numbers have more base 7 digits than base 10 digits. %K A055866 base,nonn %O A055866 2,2 %A A055866 _Jud McCranie_, May 13 2000