A354926 a(n) = 1 if n is a product of three distinct primes, otherwise 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, 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

Links

Antti Karttunen, Table of n, a(n) for n = 1..100000

Index entries for characteristic functions

Index entries for sequences computed from exponents in factorization of n

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.

Cf. A001221, A001222, A008966, A101605, A340369.

Sequence in context: A358754 A354996 A351539 * A011743 A011742 A011741

Adjacent sequences: A354923 A354924 A354925 * A354927 A354928 A354929

Keyword

nonn

Author

Antti Karttunen, Jun 13 2022

Status

approved