This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%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