A229110 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

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.

FORMULA

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

PROG

(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

CROSSREFS

Cf. A024816, A054024.

Sequence in context: A064380 A290732 A353201 * A229949 A126214 A126801

Adjacent sequences: A229107 A229108 A229109 * A229111 A229112 A229113

KEYWORD

nonn,easy

AUTHOR

Jaroslav Krizek, Sep 22 2013

STATUS

approved