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 A034848 #20 May 13 2018 17:23:35
%S A034848 73,97,103,193,229,241,277,283,313,331,367,373,397,433,457,463,547,
%T A034848 607,619,643,661,709,727,733,739,757,823,859,883,907,967,997,1021,
%U A034848 1033,1069,1087,1093,1123,1129,1171,1237,1249,1303,1423,1447,1453,1483,1489,1543,1579,1597
%N A034848 a(n) = 1 + 3*A034782(n).
%C A034848 a(n) = P(n,3) = 1 + 3*K(n,3) = 1 + 3*A034782(n). P(n,3) are special primes of the form 3k+1. The relevant values of k are given by A034782.
%C A034848 Note that, e.g., 13, 19, 31, 5, 13 are not in this sequence.
%o A034848 (PARI) a034693(n) = my(s=1); while(!isprime(s*n+1), s++); s;
%o A034848 isok(n) = a034693(n) == 3;
%o A034848 lista(nn) = {for (n=1, nn, if (isok(n), print1(3*n+1, ", ")););} \\ _Michel Marcus_, May 13 2018
%Y A034848 Cf. A034693, A034694, A034782.
%K A034848 nonn
%O A034848 1,1
%A A034848 _Labos Elemer_
%E A034848 Corrected (wrong term 769 removed) and extended by _Michel Marcus_, May 13 2018