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Numbers n such that A000005(n) <> 4.
3

%I #8 Jan 07 2013 18:26:19

%S 1,2,3,4,5,7,9,11,12,13,16,17,18,19,20,23,24,25,28,29,30,31,32,36,37,

%T 40,41,42,43,44,45,47,48,49,50,52,53,54,56,59,60,61,63,64,66,67,68,70,

%U 71,72,73,75,76,78,79,80,81,83,84,88,89,90,92,96

%N Numbers n such that A000005(n) <> 4.

%e 6 is not in the sequence because 6 has four divisors: 1, 2, 3, 6.

%t Select[Range[100],DivisorSigma[0,#]!=4&] (* _Harvey P. Dale_, Jan 07 2013 *)

%Y Complement of A030513. Column 4 of A210976.

%Y Cf. A018252, A213367.

%K nonn

%O 1,2

%A _Omar E. Pol_, Aug 11 2012