A139805 A number n is included if (product{k|n, k<=sqrt(n)} k) (= A072499(n)) does not divide n.

20, 28, 36, 42, 44, 48, 52, 54, 60, 66, 68, 72, 76, 78, 80, 84, 88, 90, 92, 96, 99, 100, 102, 104, 108, 110, 112, 114, 116, 117, 120, 124, 126, 130, 132, 136, 138, 140, 144, 148, 150, 152, 153, 156, 160, 162, 164, 168, 170, 171, 172, 174, 176, 180, 184, 186, 188

Offset: 1

Author

Leroy Quet, May 22 2008

Keywords

• nonn

Examples

			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.
		

Crossrefs

Cf. A072499.

Programs

Maple

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

Mathematica

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

Extensions

More terms from R. J. Mathar and Stefan Steinerberger, May 24 2008