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 A106217 #3 Mar 30 2012 18:36:45 %S A106217 0,3,24,30,48,57,63,72,81,99,105,114,120,129,132,135,141,147,156,159, %T A106217 168,177,180,195,198,201,204,207,210,222,243,249,252,261,267,279,282, %U A106217 285,297,309,312,315,327,333,342,351,375,387,393,399,402,408,411,414 %N A106217 Positions of 1's in A106216. %F A106217 a(n) = 0 (mod 3) for all n. %o A106217 (PARI) %Y A106217 Cf. A106216, A106218, A106219. %K A106217 nonn %O A106217 0,2 %A A106217 _Paul D. Hanna_, May 01 2005