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A190108 Numbers with prime factorization p*q*r^3*s^3 (where p, q, r, s are distinct primes). 6
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 26 16:15 EDT 2021. Contains 347670 sequences. (Running on oeis4.)