A385625 Sum of the divisors d of n with an odd number of primes not exceeding d.
0, 2, 0, 2, 5, 8, 0, 2, 0, 7, 11, 20, 0, 2, 5, 2, 17, 26, 0, 7, 0, 13, 23, 44, 30, 28, 27, 30, 0, 13, 31, 34, 44, 53, 40, 74, 0, 2, 0, 7, 41, 50, 0, 13, 5, 25, 47, 92, 49, 82, 68, 80, 0, 53, 16, 30, 0, 2, 59, 85, 0, 33, 0, 34, 5, 52, 67, 121, 92, 112, 0, 98, 73, 76, 105, 78, 88, 112, 0, 7, 27, 43, 83, 174, 107, 88, 87, 101, 0, 31, 0, 25, 31, 49, 5, 124, 97, 149
Offset: 1
Examples
The sum of the divisors d of 12 such that pi(d) is odd gives 2 + 6 + 12 = 20.
Programs
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Mathematica
Table[Sum[d*Mod[PrimePi[d], 2], {d, Divisors[n]}], {n, 100}]
Comments