A245909 - OEIS

%I #16 Sep 08 2022 08:46:09

%S 1,2,2,3,4,3,2,3,4,4,4,4,3,4,4,4,3,5,5,4,3,5,4,3,3,3,4,5,4,4,4,4,5,5,

%T 5,5,4,5,3,3,4,5,6,4,4,4,7,4,4,5,4,5,4,4,3,5,5,4,6,5,5,3,5,5,4,4,6,5,

%U 5,5,4,5,5,6,5,3,4,5,4,4,5,5,6,4,5,5,4

%N The number of distinct prime factors of prime(n)^3-1.

%H Jens Kruse Andersen, <a href="/A245909/b245909.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A001221(A030078(n)-1).

%p A245909 := proc(n)

%p     A001221(ithprime(n)^3-1) ;

%p end proc:

%t Table[PrimeNu[Prime[n]^3 - 1], {n, 100}] (* _Vincenzo Librandi_, Aug 06 2014 *)

%o (PARI) vector(500, n, omega(prime(n)^3-1)) \\ _Derek Orr_, Aug 05 2014

%o (Python) from sympy import primefactors,prime

%o def A245909(n):

%o ....return len(primefactors(prime(n)**3-1)) # _Chai Wah Wu_, Aug 05 2014

%o (Magma) [#PrimeDivisors(p^3-1): p in PrimesUpTo(500)]; // _Bruno Berselli_, Aug 06 2014

%K nonn

%O 1,2

%A _R. J. Mathar_, Aug 05 2014