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A177425
Integers with multiple and strictly distinct powers.
4
12, 18, 20, 24, 28, 40, 44, 45, 48, 50, 52, 54, 56, 63, 68, 72, 75, 76, 80, 88, 92, 96, 98, 99, 104, 108, 112, 116, 117, 124, 135, 136, 144, 147, 148, 152, 153, 160, 162, 164, 171, 172, 175, 176, 184, 188, 189, 192, 200, 207, 208, 212, 224, 232, 236, 242, 244, 245
OFFSET
1,1
COMMENTS
12=2^2*3, 18=2*3^2,.. 600=2^3*3*5^2,..
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
Apart from its first term, A001749 is a subsequence.
Cf. A001358.
Sequence in context: A375934 A332785 A367589 * A182854 A348097 A345381
KEYWORD
nonn,easy
AUTHOR
STATUS
approved