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 A140489 #2 Mar 31 2012 20:02:06 %S A140489 1,2,3,5,12,15,17,24,27,29,35,36,39,41,45,48,51,53,60,63,65,72,75,77, %T A140489 84,87,89,95,96,99,101,105,108,111,113,120,123,125,132,135,137,144, %U A140489 147,149,155,156,159,161,165,168,171,173,180,183,185,192,195 %N A140489 Numbers that cannot be part of the trajectory of any number under repeated application of the map: n -> n + second-smallest number that does not divide n, unless they are the first term of the trajectory. %Y A140489 Cf. A140485-A140488. %K A140489 nonn %O A140489 1,2 %A A140489 _Jacques Tramu_, Jun 25 2008