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A319246
Sum of prime indices of the n-th squarefree number.
6
0, 1, 2, 3, 3, 4, 4, 5, 6, 5, 5, 7, 8, 6, 6, 9, 7, 10, 6, 11, 7, 8, 7, 12, 9, 8, 13, 7, 14, 10, 15, 9, 16, 8, 10, 11, 17, 18, 12, 9, 8, 19, 11, 8, 20, 21, 13, 9, 9, 22, 14, 23, 10, 15, 12, 24, 10, 13, 16, 11, 25, 26, 10, 27, 9, 17, 28, 29, 9, 14, 30, 11, 12
OFFSET
1,3
COMMENTS
A prime index of n is a number m such that prime(m) divides n.
EXAMPLE
The 19th squarefree number is 30 with prime indices (3,2,1), so a(19) = 6.
MATHEMATICA
Table[Total[Cases[FactorInteger[n], {p_, k_}:>k*PrimePi[p]]], {n, Select[Range[100], SquareFreeQ]}]
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 15 2018
STATUS
approved