The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A139805 A number n is included if (product{k|n, k<=sqrt(n)} k) (= A072499(n)) does not divide n. 0

%I #9 Sep 16 2015 13:14:25

%S 20,28,36,42,44,48,52,54,60,66,68,72,76,78,80,84,88,90,92,96,99,100,

%T 102,104,108,110,112,114,116,117,120,124,126,130,132,136,138,140,144,

%U 148,150,152,153,156,160,162,164,168,170,171,172,174,176,180,184,186,188

%N A number n is included if (product{k|n, k<=sqrt(n)} k) (= A072499(n)) does not divide n.

%e The divisors of 42 that are each <= sqrt(42) are 1,2,3,6. The product of these is 36. 36 does not divide 42, so 42 is in the sequence.

%p A072499 := proc(n) local a,k ; a := 1 ; for k in numtheory[divisors](n) do if k^2 <= n then a := a*k ; fi ; od: a ; end: isA139805 := proc(n) RETURN( n mod A072499(n) <> 0 ) end: for n from 1 to 300 do if isA139805(n) then printf("%d,",n) ; fi ; od: # _R. J. Mathar_, May 24 2008

%t a = {}; For[n = 1, n < 200, n++, If[Mod[n,Times @@ (Select[Divisors[n], ! # > Sqrt[n] &])] > 0, AppendTo[a, n]]]; a (* _Stefan Steinerberger_ *)

%Y Cf. A072499.

%K nonn

%O 1,1

%A _Leroy Quet_, May 22 2008

%E More terms from _R. J. Mathar_ and _Stefan Steinerberger_, May 24 2008

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

Last modified November 28 19:28 EST 2023. Contains 367419 sequences. (Running on oeis4.)