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
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
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Jul 23 2010
STATUS
approved