OFFSET
1,13
COMMENTS
FORMULA
EXAMPLE
9193 has prime indices {10, 66} with product 660, which has 4 distinct prime factors {2, 3, 5, 11}, so a(9193) = 4.
MATHEMATICA
Table[PrimeNu[If[n==1, 1, Times@@PrimePi/@First/@FactorInteger[n]]], {n, 100}]
PROG
(PARI) a(n) = my(v = factor(n)[, 1]); omega(prod(i = 1, #v, primepi(v[i]))) \\ David A. Corneth, Dec 29 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 28 2018
STATUS
approved