%I
%S 9,12,13,27,28,30,36,39,40,81,82,84,90,91,108,117,120,121,243,244,246,
%T 252,270,273,324,328,351,360,363,364,729,730,732,738,756,757,810,819,
%U 820,949,972,984,1036,1053,1080,1089,1092,1093,2187
%N Numbers n with the property that some of the fractions i/n (with gcd(i,n)=1, 0 < i/n < 1) are in the Cantor set and some are not.
%C Equals A054591 \ {1,3,4,10}.
%C The natural numbers may be divided into three sets: denominators which force membership in the Cantor set, denominators which deny membership in the Cantor set and denominators which neither force nor deny membership. The first set contains just the numbers 1, 3, 4, 10. The second set is A170944. The third set is the present sequence.
%e 1/9 is in the Cantor set, but 4/9 is not.
%Y Cf. A005823, A005836, A054591, A121153, A170943, A170944.
%K nonn,base
%O 1,1
%A _J. H. Conway_ and _N. J. A. Sloane_, Feb 20 2010
