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A354926
a(n) = 1 if n is a product of three distinct primes, otherwise 0.
2
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
OFFSET
1
FORMULA
a(n) = [A001221(n) == 3] * [A001222(n) == 3], where [ ] is the Iverson bracket.
a(n) = A008966(n) * A101605(n).
For all n >= 1, a(n) <= A340369(n).
MATHEMATICA
a[n_] := If[FactorInteger[n][[;; , 2]] == {1, 1, 1}, 1, 0]; Array[a, 100] (* Amiram Eldar, Jun 13 2022 *)
PROG
(PARI) A354926(n) = ((3==bigomega(n)) && (3==omega(n)));
CROSSREFS
Characteristic function of A007304.
Sequence in context: A358754 A354996 A351539 * A011743 A011742 A011741
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jun 13 2022
STATUS
approved