A189989 Numbers with prime factorization pqrs^2t^2.

13860, 16380, 21420, 23100, 23940, 25740, 27300, 28980, 32340, 33660, 34650, 35700, 36036, 36540, 37620, 38220, 39060, 39780, 39900, 40950, 42900, 44460, 45540, 46620, 47124, 48300, 48510, 49980, 50820, 51660, 52668, 53550, 53820, 54180

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 03 2011

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

Crossrefs

Cf. A179700, A189984, A189985.

Programs

Mathematica

f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,1,2,2}; Select[Range[200000],f]

PARI

list(lim)=my(v=List(),t1,t2,t3,t4); forprime(p=2,sqrtint(lim\420), t1=p^2; forprime(q=2,sqrtint(lim\(30*t1)), if(q==p, next); t2=q^2*t1; forprime(r=2,lim\(6*t2), if(r==p || r==q, next); t3=r*t2; forprime(s=2,lim\(2*t3), if(s==p || s==q || s==r, next); t4=s*t3; forprime(t=2,lim\t4, if(t==p || t==q || t==r || t==s, next); listput(v, t4*t)))))); Set(v) \\ Charles R Greathouse IV, Aug 25 2016