OFFSET
1,1
COMMENTS
The numbers of terms that do not exceed 10^k, for k = 2, 3, ..., are 26, 344, 3762, 38711, 390527, 3915874, 39192197, 392025578, 3920580540, ... . Apparently, the asymptotic density of this sequence exists and equals 0.392... . - Amiram Eldar, Sep 25 2024
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
72 = 2^3 * 3^2 is not in the sequence because 3 and 2 are pairwise indivisible.
MATHEMATICA
Select[Range[100], !Select[Tuples[Last/@FactorInteger[#], 2], And[UnsameQ@@#, Divisible@@#]&]=={}&]
PROG
(PARI) is(k) = if(k == 1, 0, my(e = Set(factor(k)[, 2])); if(vecmax(e) == 1, 0, for(i = 1, #e, for(j = 1, i-1, if(!(e[i] % e[j]), return(1)))); 0)); \\ Amiram Eldar, Sep 25 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Aug 01 2018
STATUS
approved