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A179696 Numbers with prime signature {7,1,1}, i.e., of form p^7*q*r with p, q and r prime. 6
1920, 2688, 4224, 4480, 4992, 6528, 7040, 7296, 8320, 8832, 9856, 10880, 11136, 11648, 11904, 12160, 14208, 14720, 15232, 15744, 16512, 17024, 18048, 18304, 18560, 19840, 20352, 20608, 21870, 22656, 23424, 23680, 23936, 25728, 25984, 26240, 26752, 27264 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Will Nicholes Prime Signatures

OEIS Wiki, Numbers with same prime signature.

MAPLE

a:= proc(n) option remember; local k;

      for k from 1+ `if` (n=1, 1, a(n-1))

        while sort (map (x-> x[2], ifactors(k)[2]), `>`)<>[7, 1, 1]

      do od; k

    end:

seq (a(n), n=1..40); # Alois P. Heinz, Jan 23 2011

MATHEMATICA

f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 7}; Select[Range[30000], f]

PROG

(PARI) list(lim)=my(v=List(), t1, t2); forprime(p=2, (lim\6)^(1/7), t1=p^7; forprime(q=2, lim\t1, if(p==q, next); t2=t1*q; forprime(r=q+1, lim\t2, if(p==r, next); listput(v, t2*r)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 20 2011

CROSSREFS

Cf. A006881, A007304, A065036, A085986, A085987, A092759, A178739, A179642, A179643, A179644, A179645, A179646, A179664, A179665, A179666, A179667, A179668, A179669, A179670, A179671, A179672, A179688, A179689, A179690, A179691, A179692, A179693, A179694, A179695.

Sequence in context: A222928 A309031 A077087 * A249840 A061374 A282474

Adjacent sequences:  A179693 A179694 A179695 * A179697 A179698 A179699

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Jul 24 2010

EXTENSIONS

Title edited by Daniel Forgues, Jan 22 2011

STATUS

approved

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Last modified October 15 04:33 EDT 2019. Contains 328026 sequences. (Running on oeis4.)