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 A248874 #27 Mar 17 2015 18:05:24
%S A248874 11,61,5,41,521,101,191,331,1181,9091,13421,19141,2411,71,31,1531,
%T A248874 61681,9041,2251,152381,185641,224071,211,5791,9161,431,1021,271,
%U A248874 53951,401,71261,21821,251,4051,1151041,259631,132631,241,6781,1824841,2031671,41011
%N A248874 Primitive prime factors of the cyclotomic polynomial sequence Phi(10,k) in the order in which they occur.
%C A248874 Phi(10,k) = k^4 - k^3 + k^2 - k + 1.
%C A248874 Note that except for a(3), all terms end with the digit 1.
%H A248874 Robert Price, <a href="/A248874/b248874.txt">Table of n, a(n) for n = 1..1218</a>
%t A248874 prim = {}; Do[prim = Join[prim, Complement[First /@ FactorInteger[Cyclotomic[10, k]], prim]], {k, 1000}]; prim
%Y A248874 Cf. A005529.
%K A248874 nonn
%O A248874 1,1
%A A248874 _Robert Price_, Mar 14 2015