Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #22 Aug 07 2021 15:00:05
%S 21,30,42,66,70,84,93,102,105,110,138,154,156,165,170,186,210,217,230,
%T 231,238,255,273,282,310,318,322,330,336,345,357,364,372,374,381,385,
%U 390,399,400,420,426,434,462,465,470,483,506,510,525,530,546,561,570,595,630,642,651,658,660,682,690,705,710,714
%N Numbers k such that sigma(k) has fewer distinct prime factors than k.
%C Numbers k for which A058062(k) < A001221(k).
%C If terms x and y are present and gcd(x,y) = 1, then x*y is present also.
%t Select[Range[800],PrimeNu[#]>PrimeNu[DivisorSigma[1,#]]&] (* _Harvey P. Dale_, Aug 07 2021 *)
%Y Cf. A336355 (characteristic function), A336358 (complement).
%Y Cf. also A055743, A336359.
%K nonn
%O 1,1
%A _Antti Karttunen_, Jul 20 2020