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A108868 Numbers n such that n^5 + 3 is semiprime.

%I A108868 #9 Aug 20 2019 02:17:00
%S A108868 1,2,4,6,11,14,18,19,24,31,32,38,40,46,50,55,59,70,74,76,84,92,96,100,
%T A108868 115,119,128,139,148,150,151,154,155,158,164,178,184,200,203,204,206,
%U A108868 210,230,236,238,239,242,248,256,263,272,278,284,295,299,304,306,310
%N A108868 Numbers n such that n^5 + 3 is semiprime.
%C A108868 Note that n^5 + 3 is irreducible over integers, unlike n^5 + 1 as in A104238.
%e A108868 1^5 + 3 = 4 = 2 * 2
%e A108868 2^5 + 3 = 35 = 5 * 7
%e A108868 4^5 + 3 = 1027 = 13 * 79
%e A108868 6^5 + 3 = 7779 = 3 * 2593
%e A108868 11^5 + 3 = 161054 = 2 * 80527
%e A108868 14^5 + 3 = 89 * 6043
%e A108868 100^5 + 3 = 10000000003 = 7 * 1428571429
%e A108868 1000^5 + 3 = 1000000000000003 = 14902357 * 67103479
%e A108868 1000000^5 + 3 = 1000000000000000000000000000003 = 1859827 * 537684419034673655130289.
%p A108868 with(numtheory): a:=proc(n) if bigomega(n^5+3)=2 then n else fi end: seq(a(n),n=1..400); # _Emeric Deutsch_, Jul 16 2005
%t A108868 Select[Range[400],PrimeOmega[#^5+3]==2&] (* _Harvey P. Dale_, Jul 16 2017 *)
%Y A108868 Cf. A104238, A108814.
%K A108868 easy,nonn
%O A108868 1,2
%A A108868 _Jonathan Vos Post_, Jul 12 2005
%E A108868 More terms from _Emeric Deutsch_, Jul 16 2005