login
A345446
Number of semiprime divisors of n whose square does not divide n.
0
0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 2, 0, 1, 1, 0, 0, 2, 0, 2, 1, 1, 0, 2, 1, 1, 1, 2, 0, 3, 0, 0, 1, 1, 1, 2, 0, 1, 1, 2, 0, 3, 0, 2, 2, 1, 0, 1, 1, 2, 1, 2, 0, 2, 1, 2, 1, 1, 0, 4, 0, 1, 2, 0, 1, 3, 0, 2, 1, 3, 0, 2, 0, 1, 2, 2, 1, 3, 0, 1, 0, 1, 0, 4, 1, 1, 1, 2, 0, 4, 1, 2, 1, 1
OFFSET
1,12
COMMENTS
a(p) = 0 for p prime.
FORMULA
a(n) = Sum_{d|n} [Omega(d) = 2] * (ceiling(n/d^2) - floor(n/d^2)), where [ ] is the Iverson bracket.
MATHEMATICA
Table[Count[Select[Divisors[n], PrimeOmega[#]==2&], _?(!IntegerQ[n/#^2]&)], {n, 120}] (* Harvey P. Dale, Aug 10 2023 *)
CROSSREFS
Sequence in context: A242444 A236441 A327695 * A354911 A367098 A343660
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jun 19 2021
STATUS
approved