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A245909
The number of distinct prime factors of prime(n)^3-1.
2
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, 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, 5, 5, 4, 5, 5, 6, 5, 3, 4, 5, 4, 4, 5, 5, 6, 4, 5, 5, 4
OFFSET
1,2
LINKS
FORMULA
a(n) = A001221(A030078(n)-1).
MAPLE
A245909 := proc(n)
A001221(ithprime(n)^3-1) ;
end proc:
MATHEMATICA
Table[PrimeNu[Prime[n]^3 - 1], {n, 100}] (* Vincenzo Librandi, Aug 06 2014 *)
PROG
(PARI) vector(500, n, omega(prime(n)^3-1)) \\ Derek Orr, Aug 05 2014
(Python) from sympy import primefactors, prime
def A245909(n):
....return len(primefactors(prime(n)**3-1)) # Chai Wah Wu, Aug 05 2014
(Magma) [#PrimeDivisors(p^3-1): p in PrimesUpTo(500)]; // Bruno Berselli, Aug 06 2014
CROSSREFS
Sequence in context: A352286 A352259 A375207 * A077769 A286543 A285732
KEYWORD
nonn
AUTHOR
R. J. Mathar, Aug 05 2014
STATUS
approved