OFFSET
1,1
COMMENTS
12=2^2*3, 18=2*3^2,.. 600=2^3*3*5^2,..
LINKS
Lei Zhou, Table of n, a(n) for n = 1..10000
FORMULA
a(n) << n log n. - Charles R Greathouse IV, Mar 25 2014
MATHEMATICA
f[n_]:=Sort[Last/@FactorInteger[n]]; lst={}; Do[If[Length[f[n]]>1&&f[n]==Union@f[n], AppendTo[lst, n]], {n, 0, 6!}]; lst
PROG
(PARI) is(n)=my(f=vecsort(factor(n)[, 2]~)); n>1 && Set(f)==f && #f>1 \\ Charles R Greathouse IV, Mar 20 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vladimir Joseph Stephan Orlovsky, May 07 2010
STATUS
approved