A379958 a(n) = 1 if n has more semiprime divisors than distinct prime factors, 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, 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, 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, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 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, 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) = [A086971(n) > A001221(n)], where [ ] is the Iverson bracket.

Example

36 = 2^2 * 3^2 has three divisors (4, 6, 9) that are semiprimes, and only two prime factors (2 and 3), therefore a(36) = 1.

Prog

(PARI) A379958(n) = ((#select(d->2==bigomega(d), divisors(n))) > omega(n));

Crossrefs

Characteristic function of A320632.

Cf. A001221, A001222, A086971.

First differs from A322437 and A322438 at n=120, here a(120) = 1.

Sequence in context: A025466 A072769 A353625 * A304572 A070204 A011745

Adjacent sequences: A379955 A379956 A379957 * A379959 A379960 A379961

Keyword

nonn

Author

Antti Karttunen, Jan 24 2025

Status

approved