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 A019348 #14 Mar 31 2014 04:08:22 %S A019348 2,19,23,29,31,53,71,97,103,107,113,137,139,149,157,179,181,191,197, %T A019348 223,233,239,263,271,281,307,313,317,347,359,389,397,401,409,431,443, %U A019348 449,491,523,557,569,577,607,619,643,653,659,683,701,727,733,743,769,787,809,811 %N A019348 Primes with primitive root 21. %H A019348 Vincenzo Librandi, <a href="/A019348/b019348.txt">Table of n, a(n) for n = 1..1000</a> %H A019348 <a href="/index/Pri#primes_root">Index entries for primes by primitive root</a> %t A019348 pr=21; Select[Prime[Range[200]], MultiplicativeOrder[pr, # ] == #-1 &] %K A019348 nonn %O A019348 1,1 %A A019348 _David W. Wilson_