OFFSET
1,4
COMMENTS
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
FORMULA
Totally additive with a(prime(k)) = 2 - k.
EXAMPLE
For n = 1050 we have 5 prime indices {1,2,3,3,4}, so a(1050) = 10 - 13 = -3.
MATHEMATICA
Table[2*PrimeOmega[n]-Total[Cases[FactorInteger[n], {p_, k_}:>k*PrimePi[p]]], {n, 100}]
CROSSREFS
KEYWORD
sign
AUTHOR
Gus Wiseman, Aug 04 2021
STATUS
approved