A074941 a(n) = sigma(n) mod 3.

1, 0, 1, 1, 0, 0, 2, 0, 1, 0, 0, 1, 2, 0, 0, 1, 0, 0, 2, 0, 2, 0, 0, 0, 1, 0, 1, 2, 0, 0, 2, 0, 0, 0, 0, 1, 2, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 2, 1, 0, 0, 2, 0, 0, 0, 0, 0, 2, 0, 1, 2, 0, 0, 2, 0, 1, 0, 0, 2, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 2, 0, 0, 1, 0, 0, 2, 0, 0

Offset: 1

Author

Benoit Cloitre, Oct 04 2002

Keywords

• easy
• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384

Crossrefs

Cf. A000203, A010872.

Differs from A002324 for the first time at n=49, where a(49) = 0, while A002324(49) = 3.

Programs

Maple

A074941:= n-> (numtheory[sigma](n) mod 3):
seq (A074941(n), n=1..105); # Jani Melik, Jan 26 2011

Mathematica

a[n_] := Mod[DivisorSigma[1, n], 3]; Array[a, 100] (* Amiram Eldar, Jun 06 2022 *)

PARI

a(n)=sigma(n)%3

Formula

a(n) = A010872(A000203(n)). - Antti Karttunen, Nov 05 2017