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

1,1

Links

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

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 *)

Prog

(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

Crossrefs

Cf. A046317, A046406.

Sequence in context: A185689 A309413 A378717 * A234498 A147577 A211133

Adjacent sequences: A046387 A046388 A046389 * A046391 A046392 A046393

Keyword

nonn

Author

Patrick De Geest, Jun 15 1998

Status

approved