A353815 a(n) = 1 if sigma(n) is not a multiple of 3, otherwise 0.

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

Offset

1

Comments

a(n) = 1 iff in the prime factorization of n, all primes == 1 (mod 3) occur to odd powers, and all primes == 2 (mod 3) occur to even powers.

Links

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

Index entries for characteristic functions

Index entries for sequences related to sigma(n)

Formula

a(n) = A011655(A000203(n)).

a(n) = [A074941(n) > 0], where [ ] is the Iverson bracket.

a(n) <= A353816(n).

Mathematica

a[n_] := If[!Divisible[DivisorSigma[1, n], 3], 1, 0]; Array[a, 100] (* Amiram Eldar, May 15 2022 *)

Prog

(PARI) A353815(n) = (0!=(sigma(n)%3));

Crossrefs

Characteristic function of A329963.

Cf. A000203, A011655, A074941, A353816.

Sequence in context: A266502 A075438 A118174 * A156258 A132138 A141212

Adjacent sequences: A353812 A353813 A353814 * A353816 A353817 A353818

Keyword

nonn

Author

Antti Karttunen, May 15 2022

Status

approved