A190108 Numbers with prime factorization p*q*r^3*s^3 (where p, q, r, s are distinct primes).

7560, 11880, 14040, 16632, 18360, 19656, 20520, 21000, 24840, 25704, 28728, 30888, 31320, 33000, 33480, 34776, 39000, 39960, 40392, 41160, 43848, 44280, 45144, 46440, 46872, 47250, 47736, 50760, 51000, 53352, 54648, 55944, 57000, 57240, 61992, 63720, 64584

Offset

1,1

Comments

A050326(a(n)) = 11. - 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

Example

From Petros Hadjicostas, Oct 26 2019: (Start)
a(1) = (2^3)*(3^3)*5*7 = 7560;
a(2) = (2^3)*(3^3)*5*11 = 11880;
a(3) = (2^3)*(3^3)*5*13 = 14040;
a(4) = (2^3)*(3^3)*7*11 = 16632.
(End)

Mathematica

f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 3, 3}; Select[Range[150000], f]

Prog

(PARI) list(lim)=my(v=List(), t1, t2, t3); forprime(p=2, sqrtnint(lim\120, 3), t1=p^3; forprime(q=2, sqrtnint(lim\(6*t1), 3), if(q==p, next); t2=q^3*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

Cf. A179704, A190106, A190107.

Sequence in context: A234987 A157322 A172443 * A308913 A145313 A235961

Adjacent sequences: A190105 A190106 A190107 * A190109 A190110 A190111

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, May 04 2011

Extensions

Name edited by Petros Hadjicostas, Oct 26 2019

Status

approved