A179693 Numbers of the form p^4*q*r*s where p, q, r, and s are distinct primes.

1680, 2640, 3120, 3696, 4080, 4368, 4560, 5520, 5670, 5712, 6160, 6384, 6864, 6960, 7280, 7440, 7728, 8880, 8910, 8976, 9520, 9744, 9840, 10032, 10320, 10416, 10530, 10608, 10640, 11280, 11440, 11856, 12144, 12432, 12474, 12720, 12880, 13770

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Jul 24 2010

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• Will Nicholes, Prime Signatures
• Index to sequences related to prime signature

Programs

Mathematica

f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,1,4}; Select[Range[15000], f]
Take[Union[First[#]^4 Times@@Rest[#]&/@Flatten[ Permutations/@ Subsets[ Prime[Range[20]],{4}],1]],50] (* Harvey P. Dale, Jan 26 2013 *)

PARI

list(lim)=my(v=List(),t1,t2,t3); forprime(p=2,sqrtnint(lim\30, 4), t1=p^4; 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