A190107 Numbers with prime factorization pqr^2s^4.

5040, 7920, 8400, 9360, 11088, 11340, 11760, 12240, 13104, 13200, 13680, 15600, 16560, 17136, 17820, 19152, 20400, 20592, 20880, 21060, 22320, 22800, 23184, 24948, 25872, 26640, 26928, 27540, 27600, 28350, 29040, 29232, 29484, 29520

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 04 2011

Keywords

• nonn

Comments

A050326(a(n)) = 3. - 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

Crossrefs

Cf. A111467, A179704, A190106.

Programs

Mathematica

f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,2,4};Select[Range[60000],f]

PARI

list(lim)=my(v=List(),t1,t2,t3); forprime(p=2,sqrtnint(lim\60, 4), t1=p^4; 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