A046390 Squarefree odd numbers with exactly 4 distinct prime factors.

1155, 1365, 1785, 1995, 2145, 2415, 2805, 3003, 3045, 3135, 3255, 3315, 3705, 3795, 3885, 3927, 4305, 4389, 4485, 4515, 4641, 4785, 4845, 4935, 5005, 5115, 5187, 5313, 5565, 5655, 5865, 6045, 6105, 6195, 6279, 6405, 6545, 6555, 6699, 6765, 6783, 7035

Offset: 1

Author

Patrick De Geest, Jun 15 1998

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n=1..1000

Crossrefs

Cf. A046317, A046406.

Programs

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1,1,1,1}&&FactorInteger[n][[1,1]]>2; lst={};Do[If[f[n],AppendTo[lst,n]],{n,8!}];lst (* Vladimir Joseph Stephan Orlovsky, Nov 23 2009 *)
Select[Range[1,8001,2],PrimeNu[#]==PrimeOmega[#]==4&] (* Harvey P. Dale, Mar 28 2013 *)

PARI

list(lim)=my(v=List()); forprime(p=3,sqrtnint(lim\=1,4), forprime(q=p+2,sqrtnint(lim\p,3), forprime(r=q+2,sqrtint(lim\p\q), my(t=p*q*r); forprime(s=r+2,lim\t, listput(v,t*s))))); Set(v) \\ Charles R Greathouse IV, Dec 06 2024