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 A031309 #4 Mar 30 2012 18:56:23 %S A031309 1,2,3,4,5,6,7,8,9,29,11,1,15,17,19,21,23,25,27,49,14,33,2,37,39,41, %T A031309 43,45,47,69,16,36,55,3,59,61,63,65,67,89,18,38,58,77,4,81,83,85,87, %U A031309 109,20,40,60,80,99,5,103,105,107,129,22,42,62,82 %N A031309 a(n)=least k such that base 10 representation of n begins at s(k), where s=A031298. %K A031309 nonn %O A031309 1,2 %A A031309 _Clark Kimberling_