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A124876
Number of prime factors (counted with multiplicity) in factorization of A007408(n).
3
0, 2, 1, 3, 2, 4, 3, 2, 3, 5, 3, 3, 3, 2, 1, 4, 2, 5, 1, 3, 2, 6, 2, 4, 2, 1, 3, 5, 3, 6, 1, 2, 3, 2, 3, 10, 4, 4, 5, 5, 8, 7, 7, 2, 4, 7, 3, 2, 4, 3, 2, 5, 3, 4, 2, 8, 3, 4, 4, 5, 3, 3, 7, 2, 5, 10, 4, 2, 6, 8, 3, 6, 6, 4, 3, 6, 4, 7, 4, 4, 3, 4, 8, 5, 7, 4
OFFSET
1,2
LINKS
FORMULA
a(n) = A001222(A007408(n)). - R. J. Mathar, May 18 2007
EXAMPLE
a(1) = 0 since A007408(1) = 1 contains no prime factor,
a(2) = 2 since A007408(2) = 9 = 3 * 3,
a(3) = 1 since A007408(3) = 251 is prime,
a(6) = 4 since A007408(6) = 7 * 7 * 11 * 53.
MAPLE
seq( add(op(2, j), j=op(2, (ifactors@A007408)(n))), n=1..28 );
A001222 := proc(n) numtheory[bigomega](n) ; end: b := fscanf("b007408.txt", "%d %d") : while b <> [] do printf("%d, ", A001222(op(2, b))) ; b := fscanf("b007408.txt", "%d %d") : od : # R. J. Mathar, May 18 2007
MATHEMATICA
Table[PrimeOmega[Numerator[Sum[1/k^3, {k, 1, n}]]], {n, 1, 50}] (* Amiram Eldar, Feb 09 2020 *)
PrimeOmega[Numerator[Accumulate[1/Range[50]^3]]] (* Harvey P. Dale, Aug 28 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Nov 11 2006
EXTENSIONS
More terms from R. J. Mathar, May 18 2007
More terms from Amiram Eldar, Feb 09 2020
STATUS
approved