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 A031006 #4 Mar 30 2012 18:56:19 %S A031006 1,2,3,4,5,6,7,9,1,13,15,17,19,21,12,25,2,29,31,33,35,14,28,41,3,45, %T A031006 47,49,16,30,44,57,4,61,63,18,32,46,60,73,5,77,6,20,34,48,62,76,91,7, %U A031006 97,100,103,106,109,96,9,10,121,124,127,130,133,11 %N A031006 a(n)=least k such that base 7 representation of n begins at s(k), where s=A030998. %K A031006 nonn %O A031006 1,2 %A A031006 _Clark Kimberling_