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 A178389 #3 Mar 30 2012 17:40:24 %S A178389 21,69,93,141,213,237,309,381,453,501,573,597,669,717,789,813,933, %T A178389 1077,1101,1149,1293,1317,1389,1437,1461,1509,1797,1821,1893,1941, %U A178389 2157,2181,2229,2253,2469,2517,2589,2661,2733,2757,2901,2949,2973,3093,3117,3189 %N A178389 Multiples of 3 in A175461. %F A178389 a(n) = 3*A007522(n). [From _R. J. Mathar_, May 31 2010] %Y A178389 Cf. A175461. %K A178389 nonn %O A178389 1,1 %A A178389 _Zak Seidov_, May 27 2010