A353676 a(n) = 1 if n is an odd number with exactly 2 distinct prime factors, otherwise 0.

0, 0, 0, 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, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Formula

a(n) = A000035(n) * A215480(n).

A353675(n) >= a(n) >= A353677(n).

Example

n = 45 = 3^2 * 5 is an odd number with two distinct prime factors, therefore a(45) = 1.

Prog

(PARI) A353676(n) = ((n%2) && (2==omega(n)));

Crossrefs

Characteristic function of A225375.

Cf. A000035, A001221, A215480, A353677.

After n=1 differs from A353675 for the next time at n=1155, where a(1155)=0, while A353675(1155)=1.

Sequence in context: A277161 A353481 A353677 * A340370 A216038 A011728

Adjacent sequences: A353673 A353674 A353675 * A353677 A353678 A353679

Keyword

nonn

Author

Antti Karttunen, May 03 2022

Status

approved