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