A105852 a(n) = sigma(n) mod 9.

1, 3, 4, 7, 6, 3, 8, 6, 4, 0, 3, 1, 5, 6, 6, 4, 0, 3, 2, 6, 5, 0, 6, 6, 4, 6, 4, 2, 3, 0, 5, 0, 3, 0, 3, 1, 2, 6, 2, 0, 6, 6, 8, 3, 6, 0, 3, 7, 3, 3, 0, 8, 0, 3, 0, 3, 8, 0, 6, 6, 8, 6, 5, 1, 3, 0, 5, 0, 6, 0, 0, 6, 2, 6, 7, 5, 6, 6, 8, 6, 4, 0, 3, 8, 0, 6, 3, 0, 0, 0, 4, 6, 2, 0, 3, 0, 8, 0, 3, 1, 3, 0, 5, 3, 3

Offset

1,2

Comments

If gcd(m,n) = 1 then a(m*n) = (a(m) * a(n)) mod 9. - Robert Israel, Sep 14 2014

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

a(n) = A010878(A000203(n)). - Michel Marcus, Sep 14 2014

Maple

seq(numtheory:-sigma(n) mod 9, n=1..1000); # Robert Israel, Sep 14 2014

Mathematica

Mod[DivisorSigma[1, Range[100]], 9] (* Wesley Ivan Hurt, Apr 25 2023 *)

Prog

(PARI) a(n)=sigma(n)%9

Crossrefs

Cf. A000203, A010878, A190998 (digital root of sigma(n)).

Sequence in context: A017665 A389447 A248789 * A190998 A067342 A348987

Adjacent sequences: A105849 A105850 A105851 * A105853 A105854 A105855

Keyword

easy,nonn

Author

Shyam Sunder Gupta, May 05 2005

Extensions

Name corrected and keyword base removed by Michel Marcus, Sep 14 2014

Status

approved