OFFSET
1,5
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(n)) = A056239(n).
EXAMPLE
91 has prime indices {4,6} with prime indices {{1,1},{1,2}} with sum a(91) = 5.
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[Plus@@Join@@primeMS/@primeMS[n], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Mar 25 2019
STATUS
approved