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 A106218 #3 Mar 30 2012 18:36:45 %S A106218 6,9,12,21,27,33,69,75,84,87,93,96,111,123,126,162,165,192,225,228, %T A106218 231,234,237,240,264,270,273,276,288,300,306,318,321,339,345,354,357, %U A106218 360,378,381,384,390,417,426,429,432,438,441,447,453,468,471,474,477,483 %N A106218 Positions of 2's in A106216. %F A106218 a(n) = 0 (mod 3) for all n. %o A106218 (PARI) %Y A106218 Cf. A106216, A106217, A106219. %K A106218 nonn %O A106218 0,1 %A A106218 _Paul D. Hanna_, May 01 2005