A179670 Numbers of the form p^3*q*r*s where p, q, r, and s are distinct primes.

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

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

Index to sequences related to prime signature

Mathematica

f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 1, 3}; Select[Range[10000], f]
Take[#[[1]]^3 #[[2]]#[[3]]#[[4]]&/@Flatten[Permutations/@Subsets[Prime[ Range[20]], {4}], 1]//Union, 50] (* Harvey P. Dale, May 16 2021 *)

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