A177425 Integers with multiple and strictly distinct powers.

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,..

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

Apart from its first term, A001749 is a subsequence.

Cf. A001358.

Sequence in context: A317616 A332785 A367589 * A182854 A348097 A345381

Adjacent sequences: A177422 A177423 A177424 * A177426 A177427 A177428

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, May 07 2010

Status

approved