A229110 Sum of non-divisors of n reduced modulo n.

0, 0, 2, 3, 4, 3, 6, 5, 5, 7, 10, 2, 12, 11, 6, 9, 16, 6, 18, 8, 10, 19, 22, 0, 19, 23, 14, 14, 28, 3, 30, 17, 18, 31, 22, 35, 36, 35, 22, 10, 40, 9, 42, 26, 12, 43, 46, 44, 41, 32, 30, 32, 52, 15, 38, 20, 34, 55, 58, 42, 60, 59, 22, 33, 46, 21, 66, 44, 42

Offset: 1

Author

Jaroslav Krizek, Sep 22 2013

Keywords

• nonn
• easy

Comments

Numbers n such that a(n)=0 are: 1, 2, 24, 4320, 4680, ... (see A159907, conjecture by Jaroslav Krizek and further comments). - Michel Marcus, Sep 23 2013

Numbers n such that a(n)=n/2 are: 6, 28, 120, 496, 672, ... = A007691 \ {1}. - Michel Marcus, Sep 25 2013

Links

• Jaroslav Krizek, Table of n, a(n) for n = 1..10000.

Crossrefs

Cf. A024816, A054024.

Programs

Haskell

a229110 n = mod (a024816 n) n

PARI

a(n) = lift(sum(i=1, n, if (n % i, Mod(i, n), 0))); \\ Michel Marcus, Sep 23 2013

PARI

a(n)=(n*(n+1)/2-sigma(n))%n \\ Charles R Greathouse IV, Sep 23 2013

Formula

a(n) = A024816(n) mod n.