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A179693 Numbers of the form p^4*q*r*s where p, q, r, and s are distinct primes. 8
1680, 2640, 3120, 3696, 4080, 4368, 4560, 5520, 5670, 5712, 6160, 6384, 6864, 6960, 7280, 7440, 7728, 8880, 8910, 8976, 9520, 9744, 9840, 10032, 10320, 10416, 10530, 10608, 10640, 11280, 11440, 11856, 12144, 12432, 12474, 12720, 12880, 13770 (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

Index to sequences related to prime signature

MAPLE

op(select(n->nops(factorset(n))=4 and sort([seq(op(2, a), a=ifactors(n)[2])])=[1, 1, 1, 4], [$1..13770])); # Paolo P. Lava, Jul 18 2019

MATHEMATICA

f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 1, 4}; Select[Range[15000], f]

Take[Union[First[#]^4 Times@@Rest[#]&/@Flatten[ Permutations/@ Subsets[ Prime[Range[20]], {4}], 1]], 50] (* Harvey P. Dale, Jan 26 2013 *)

PROG

(PARI) list(lim)=my(v=List(), t1, t2, t3); forprime(p=2, sqrtnint(lim\30, 4), t1=p^4; forprime(q=2, lim\(6*t1), if(q==p, next); t2=q*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

Sequence in context: A268288 A175749 A231548 * A290704 A175340 A181928

Adjacent sequences:  A179690 A179691 A179692 * A179694 A179695 A179696

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Jul 24 2010

STATUS

approved

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Last modified October 17 14:31 EDT 2019. Contains 328114 sequences. (Running on oeis4.)