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A369225
Sum of the semiprimes less than n that do not divide n.
1
0, 0, 0, 0, 4, 4, 10, 6, 10, 19, 29, 19, 29, 29, 43, 54, 58, 43, 58, 44, 58, 79, 101, 91, 101, 126, 143, 134, 152, 121, 152, 148, 152, 185, 219, 235, 254, 254, 292, 317, 331, 290, 331, 305, 307, 331, 377, 367, 377, 391, 426, 447, 477, 462, 477, 514, 532, 589, 647, 612, 647, 647, 679
OFFSET
1,5
FORMULA
a(n) = Sum_{k=1..n} k * c(k) * (ceiling(n/k) - floor(n/k)), where c = A064911.
MATHEMATICA
Table[Sum[k*KroneckerDelta[PrimeOmega[k], 2] (Ceiling[n/k] - Floor[n/k]), {k, n}], {n, 100}]
CROSSREFS
Cf. A001358 (semiprimes), A064911, A369224.
Sequence in context: A353267 A339336 A319056 * A050348 A134637 A078910
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Jan 16 2024
STATUS
approved