OFFSET
1,1
COMMENTS
The asymptotic density of this sequence is 1 - Product_{p prime} ((1 - 1/p) * Sum_{i>=1} 1/p^A004709(i)) = 0.002064412516... .
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
256 = 2^8 is a term since 8 = 2^3 is not cubefree.
MATHEMATICA
noncubfreeQ[n_] := Max[FactorInteger[n][[;; , 2]]] > 2; Select[Range[2*10^4], AnyTrue[FactorInteger[#][[;; , 2]], noncubfreeQ] &]
PROG
(PARI) isnoncubefree(n) = {n > 7 && vecmax(factor(n)[, 2]) > 2; }
is(n) = {my(e = factor(n)[, 2]); for(i=1, #e, if(isnoncubefree(e[i]), return(1))); 0; }
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Mar 03 2023
STATUS
approved