This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A179670 Numbers of the form p^3*q*r*s where p, q, r, and s are distinct primes. 9
 840, 1320, 1560, 1848, 1890, 2040, 2184, 2280, 2760, 2856, 2970, 3080, 3192, 3432, 3480, 3510, 3640, 3720, 3864, 4158, 4440, 4488, 4590, 4760, 4872, 4914, 4920, 5016, 5130, 5160, 5208, 5250, 5304, 5320, 5640, 5720, 5928, 6072, 6210, 6216, 6360, 6426 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A050326(a(n)) = 7. - Reinhard Zumkeller, May 03 2013 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 Will Nicholes, Prime Signatures MAPLE op(select(n->nops(factorset(n))=4 and sort([seq(op(2, a), a=ifactors(n)[2])])=[1, 1, 1, 3], [\$1..6426])); # Paolo P. Lava, Jul 18 2019 MATHEMATICA f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 1, 3}; Select[Range[10000], f] PROG (PARI) list(lim)=my(v=List(), t1, t2, t3); forprime(p=2, sqrtnint(lim\30, 3), t1=p^3; forprime(q=2, lim\(6*t1), if(q==p, next); t2=q*t1; forprime(r=2, lim\(2*t2), if(r==p || r==q, next); t3=r*t2; forprime(s=2, lim\t3, if(s==p || s==q || s==r, next); listput(v, t3*s))))); Set(v) \\ Charles R Greathouse IV, Aug 25 2016 CROSSREFS Sequence in context: A068546 A033269 A272595 * A092002 A169827 A158402 Adjacent sequences:  A179667 A179668 A179669 * A179671 A179672 A179673 KEYWORD nonn AUTHOR Vladimir Joseph Stephan Orlovsky, Jul 23 2010 STATUS approved

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.

Last modified October 17 14:31 EDT 2019. Contains 328114 sequences. (Running on oeis4.)