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 A118640 #4 Oct 12 2013 15:24:51 %S A118640 1,6,16,66,166,666,1666,6666,16666,66666,166666,666666 %N A118640 Result of left concatenation of the next Roman-numeral symbol. %e A118640 a(1) = I; a(2) = VI; a(3) = XVI. %K A118640 easy,nonn,base,fini,full %O A118640 1,2 %A A118640 _Greg Huber_, May 09 2006 %E A118640 Edited by _Charles R Greathouse IV_, Apr 25 2010