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 A186721 #11 Oct 30 2018 10:31:02
%S A186721 3,7,13,37,73,277,373,577,727,853,1033,1063,1327,1423,1453,1567,1777,
%T A186721 1987,2293,2677,2767,3037,3163,3307,3457,4273,4447,4993,5197,5557,
%U A186721 6247,6673,7573,8353,8893,9067,9397,9463,9547,9613,10303,10903,12007,12973,13177,14083
%N A186721 Numbers n such that n, 4n + 1 and 6n + 1 are all prime.
%C A186721 Subsequence of A023212.
%t A186721 Join[{3},Select[Range[7, 20000, 6], PrimeQ[#] && PrimeQ[4# + 1] && PrimeQ[6# + 1] &]]
%Y A186721 Cf. A023212.
%K A186721 nonn
%O A186721 1,1
%A A186721 _Zak Seidov_, Jan 21 2012