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 A050130 #4 Mar 30 2012 18:57:01 %S A050130 2,4,5,7,10,11,13,16,18,21,23,25,28,30,33,35,38,41,43,45,47,49,52,54, %T A050130 57,59,62,65,67,69,72,74,77,79,82,83,85,87,89,92,94,95,97,100,102,105, %U A050130 107,110,113,115,117,120,122,125,127,130,131 %N A050130 a(n)=least k satisfying a(k)=2*k in A050128. %K A050130 nonn %O A050130 1,1 %A A050130 _Clark Kimberling_