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%I #14 Oct 08 2020 03:26:47
%S 1,2,4,6,8,9,12,16,18,20,24,27,30,32,36,40,42,45,48,50,54,56,60,64,70,
%T 72,75,80,81,84,90,96,100,105,108,112,120,126,128,132,135,140,144,150,
%U 160,162,168,180,189,192,196,198,200,210,216,220,224,225,240,243,250
%N Numbers k whose prime divisors are all less than or equal to the number of divisors of k.
%C Density: 33 terms between 1 and 100, 17 between 201 and 300, 11 between 1001 and 1100, and 2 between 1000001 and 1000100.
%e 42=a(17) is a term, since 2,3 and 7 are the prime divisors of 42, which has 8 divisors. 156=2^2*3*13 is not a term, since 13 is greater than 12, the number of divisors of 156.
%t Select[Range[250], FactorInteger[#][[-1, 1]] <= DivisorSigma[0, #] &] (* _Amiram Eldar_, Sep 22 2020 *)
%o (PARI) isok(m) = #select(x->(x>numdiv(m)), factor(m)[,1]) == 0; \\ _Michel Marcus_, Sep 22 2020
%Y A199768 has "strictly less", while this sequence has "less than or equal to".
%Y The union of A199768 and A036878.
%Y A146982 does not include terms 42, 56, 132, 198, 220, 264, 308, 312, 330, ...
%Y Cf. A000005.
%K nonn
%O 1,2
%A _Richard Peterson_, Sep 15 2020