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A179642
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Product of exactly 5 primes, 3 of which are distinct.
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24
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120, 168, 180, 252, 264, 270, 280, 300, 312, 378, 396, 408, 440, 450, 456, 468, 520, 552, 588, 594, 612, 616, 680, 684, 696, 700, 702, 728, 744, 750, 760, 828, 882, 888, 918, 920, 945, 952, 980, 984, 1026, 1032, 1044, 1064, 1100, 1116, 1128, 1144, 1160
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..1000
Will Nicholes, Prime Signatures
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EXAMPLE
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120=2^3*3*5, 168=2^3*3*7, 180=2^2*3^2*5, 252=2^2*3^2*7, 264=2^3*3*11, 270=2*3^3*5
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MATHEMATICA
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f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 3} || Sort[Last/@FactorInteger[n]]=={1, 2, 2}; Select[Range[2000], f]
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PROG
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(PARI) list(lim)=my(v=List(), t); forprime(p=2, (lim\6)^(1/3), forprime(q=2, sqrt(lim\p^3), if(p==q, next); t=p^3*q; forprime(r=q+1, lim\t, if(p==r, next); listput(v, t*r)))); forprime(p=2, sqrt(lim\12), forprime(q=p+1, sqrt(lim\p^2\2), t=(p*q)^2; forprime(r=2, lim\t, if(p==r||q==r, next); listput(v, t*r)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 19 2011
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CROSSREFS
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Union of A189975 and A179643.
Cf. A006881, A007304, A085986, A085987, A178739.
Sequence in context: A192277 A034291 A039602 * A099832 A111399 A030634
Adjacent sequences: A179639 A179640 A179641 * A179643 A179644 A179645
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KEYWORD
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nonn
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AUTHOR
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Vladimir Joseph Stephan Orlovsky, Jul 21 2010
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STATUS
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approved
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