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 A123074 Number of ordered triples of primes (p,q,r) such that pqr = n. 3
 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 3, 0, 0, 0, 0, 0, 3, 0, 3, 0, 0, 0, 0, 0, 0, 1, 3, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 3, 3, 0, 0, 0, 0, 3, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 6, 0, 3, 0, 6, 0, 0, 0, 0, 3, 3, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 3, 3, 0, 0, 6, 0, 0, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,12 COMMENTS For distinct primes p, q and r, a(p^3) = 1, a(p^2 q) = 3, a(pqr) = 6, otherwise (when A101605(n) = 0), a(n) = 0. - Comment clarified by David A. Corneth and Antti Karttunen, Jul 23 2017 LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 MATHEMATICA Join[{0}, Table[e=Sort[Transpose[FactorInteger[n]][[2]]]; Which[e=={3}, 1, e=={1, 2}, 3, e=={1, 1, 1}, 6, True, 0], {n, 2, 150}]] (* T. D. Noe, Sep 29 2006 *) PROG (PARI) A123074(n) = if(3==bigomega(n), binomial(1+omega(n), 2), 0); \\ Antti Karttunen, Jul 23 2017 CROSSREFS Cf. A001221, A001222, A101605, A123073, A014612. Sequence in context: A059484 A035678 A094518 * A095269 A308275 A308254 Adjacent sequences:  A123071 A123072 A123073 * A123075 A123076 A123077 KEYWORD nonn AUTHOR N. J. A. Sloane and T. D. Noe, Sep 29 2006 EXTENSIONS More terms from T. D. Noe, Sep 29 2006 STATUS approved

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Last modified January 18 13:38 EST 2022. Contains 350455 sequences. (Running on oeis4.)