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%I #27 Aug 11 2014 23:16:39
%S 0,1,2,2,2,2,3,2,3,2,4,2,3,2,3,4,2,2,3,2,3,3,4,2,4,3,3,2,4,3,4,3,2,3,
%T 4,4,4,2,4,3,3,3,4,3,4,4,4,3,4,2,4,3,4,2,4,4,3,4,3,3,5,2,4,4,3,3,5,3,
%U 3,3,4,3,3,4,3,3,3,3,5,2
%N The number of distinct prime factors of n^3-1.
%H Jens Kruse Andersen, <a href="/A240975/b240975.txt">Table of n, a(n) for n = 1..10000</a>
%F a(prime(n)) = A245909(n).
%F a(n) = A001221(A068601(n)). - _Michel Marcus_, Aug 06 2014
%e 3^3-1 = 26 = 2*13, so a(3)=2.
%e 0 has no prime factors, so a(1)=0.
%p A240975 := proc(n)
%p A001221(n^3-1) ;
%p end proc:
%o (Python)
%o from sympy import primefactors
%o def A240975(n):
%o ....return len(primefactors(n**3-1)) # _Chai Wah Wu_, Aug 06 2014
%o (PARI) a(n) = if(n<=1,0,omega(n^3-1)); \\ _Joerg Arndt_, Aug 06 2014
%Y Cf. A082863, A245909, A001221.
%K nonn,easy
%O 1,3
%A _R. J. Mathar_, Aug 05 2014
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