login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A064052 Not sqrt(n)-smooth: some prime factor of n is > sqrt(n). 13

%I

%S 2,3,5,6,7,10,11,13,14,15,17,19,20,21,22,23,26,28,29,31,33,34,35,37,

%T 38,39,41,42,43,44,46,47,51,52,53,55,57,58,59,61,62,65,66,67,68,69,71,

%U 73,74,76,77,78,79,82,83,85,86,87,88,89,91,92,93,94,95,97,99,101,102

%N Not sqrt(n)-smooth: some prime factor of n is > sqrt(n).

%C This set (S say) has density d(S) = Log(2) - _Benoit Cloitre_, Jun 12 2002

%C Finch defines a positive integer N to be "jagged" if its largest prime factor is > sqrt(N). - _Frank Ellermann_, Apr 21 2011

%D S. R. Finch, Mathematical Constants, 2003, chapter 2.21.

%H Harry J. Smith, <a href="/A064052/b064052.txt">Table of n, a(n) for n = 1..1000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GreatestPrimeFactor.html">Greatest Prime Factor</a>

%e 9=3*3 is not "jagged", but 10=5*2 is "jagged": 5 > sqrt(10).

%e 20=5*2*2 is "jagged", but not squarefree, cf. A005117.

%t Reap[For[n = 2, n <= 102, n++, f = FactorInteger[n][[-1, 1]]; If[f > Sqrt[n], Sow[n]]]][[2, 1]] (* _Jean-Fran├žois Alcover_, May 16 2014 *)

%o (PARI) { n=0; for (m=2, 10^9, f=factor(m)~; if (f[1, length(f)]^2 > m, write("b064052.txt", n++, " ", m); if (n==1000, break)) ) } \\ _Harry J. Smith_, Sep 06 2009

%Y Cf. A048098, A063538, A063539.

%K nonn,easy

%O 1,1

%A _Dean Hickerson_, Aug 28 2001

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 13 09:48 EST 2019. Contains 329968 sequences. (Running on oeis4.)