OFFSET
1,6
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.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
FORMULA
EXAMPLE
The prime indices of 1100 are {1,1,3,3,5}, so a(1100) = 1 + 3 = 4.
The prime indices of 2100 are {1,1,2,3,3,4}, so a(2100) = 1 + 3 + 4 = 8.
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[Total[Last/@Partition[Append[primeMS[n], 0], 2]], {n, 100}]
PROG
(PARI) A346698(n) = if(1==n, 0, my(f=factor(n), s=0, p=0); for(k=1, #f~, while(f[k, 2], s += (p%2)*primepi(f[k, 1]); f[k, 2]--; p++)); (s)); \\ Antti Karttunen, Nov 30 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Aug 01 2021
EXTENSIONS
Data section extended up to 105 terms by Antti Karttunen, Nov 30 2021
STATUS
approved