# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a123074
Showing 1-1 of 1

%I A123074 #20 Oct 20 2024 12:44:13
%S A123074 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,
%T A123074 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,
%U A123074 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
%N A123074 Number of ordered triples of primes (p,q,r) such that pqr = n.
%C A123074 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
%H A123074 Antti Karttunen, <a href="/A123074/b123074.txt">Table of n, a(n) for n = 1..10000</a>
%H A123074 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>
%t A123074 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 *)
%o A123074 (PARI) A123074(n) = if(3==bigomega(n),binomial(1+omega(n),2),0); \\ _Antti Karttunen_, Jul 23 2017
%o A123074 (Python)
%o A123074 from sympy import factorint
%o A123074 def A123074(n): return (1,3,6)[len(f)-1] if sum(f:=factorint(n).values())==3 else 0 # _Chai Wah Wu_, Oct 20 2024
%Y A123074 Cf. A001221, A001222, A101605, A123073, A014612.
%K A123074 nonn
%O A123074 1,12
%A A123074 _N. J. A. Sloane_ and _T. D. Noe_, Sep 29 2006
%E A123074 More terms from _T. D. Noe_, Sep 29 2006

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE