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A179694
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Numbers of the form p^6*q^3 where p and q are distinct primes.
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4
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1728, 5832, 8000, 21952, 85184, 91125, 125000, 140608, 250047, 314432, 421875, 438976, 778688, 941192, 970299, 1560896, 1601613, 1906624, 3176523, 3241792, 3581577, 4410944, 5000211, 5088448, 5359375, 6644672
(list;
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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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FORMULA
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Sum_{n>=1} 1/a(n) = P(3)*P(6) - P(9) = A085541 * A085966 - A085969 = 0.000978..., where P is the prime zeta function. - Amiram Eldar, Jul 06 2020
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MATHEMATICA
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f[n_]:=Sort[Last/@FactorInteger[n]]=={3, 6}; Select[Range[10^6], f]
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PROG
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(PARI) list(lim)=my(v=List(), t); forprime(p=2, (lim\8)^(1/6), t=p^6; forprime(q=2, (lim\t)^(1/3), if(p==q, next); listput(v, t*q^3))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 24 2011
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CROSSREFS
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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.
Cf. A085541, A085966, A085969.
Sequence in context: A032354 A305475 A202458 * A202200 A251188 A323560
Adjacent sequences: A179691 A179692 A179693 * A179695 A179696 A179697
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KEYWORD
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nonn
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AUTHOR
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Vladimir Joseph Stephan Orlovsky, Jul 24 2010
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STATUS
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approved
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