A190474 - OEIS

%I #9 Aug 25 2016 23:12:10

%S 20160,31680,33600,37440,44352,47040,48960,52416,52800,54720,62400,

%T 66240,68544,76608,81600,82368,83520,89280,91200,92736,102060,103488,

%U 106560,107712,110400,116160,116928,118080,120384,122304,123200,123840

%N Numbers with prime factorization pqr^2s^6.

%H T. D. Noe, <a href="/A190474/b190474.txt">Table of n, a(n) for n = 1..1000</a>

%H Will Nicholes, <a href="http://willnicholes.com/math/primesiglist.htm">Prime Signatures</a>

%t f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,2,6}; Select[Range[300000],f]

%o (PARI) list(lim)=my(v=List(),t1,t2,t3); forprime(p=2,sqrtnint(lim\60, 6), t1=p^6; forprime(q=2,sqrtint(lim\(6*t1)), if(q==p, next); t2=q^2*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

%Y Cf. A190472, A190473.

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 10 2011