A232324 n(n+1)/2 modulo sigma(n).

0, 0, 2, 3, 3, 9, 4, 6, 6, 1, 6, 22, 7, 9, 0, 12, 9, 15, 10, 0, 7, 1, 12, 0, 15, 15, 18, 14, 15, 33, 16, 24, 33, 1, 6, 29, 19, 21, 52, 10, 21, 39, 22, 66, 21, 1, 24, 60, 28, 66, 30, 6, 27, 45, 28, 36, 53, 1, 30, 150, 31, 33, 40, 48, 45, 51, 34, 78, 15, 37, 36

Offset

1,3

Comments

Also antisigma(n) modulo sigma(n). Antisigma(n) = A024816(n) = the sum of the nondivisors of n that are between 1 and n, sigma(n) = A000203(n) = the sum of the divisors of n.

a(n) = 0 for numbers from A076617, a(n) = 1 for numbers from A232540, a(n) = n for numbers from A232538.

Links

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

Formula

a(n) = n(n+1)/2 mod A000203(n).

Example

For n=10, a(10) = antisigma(10) mod sigma(10) = 37 mod 18 = 1.

Mathematica

Table[Mod[n (n + 1)/2, DivisorSigma[1, n]], {n, 100}] (* T. D. Noe, Nov 27 2013 *)

Crossrefs

Cf. A000203, A076617, A024816, A232538, A232540.

Sequence in context: A166994 A059083 A207626 * A124931 A210226 A209163

Adjacent sequences: A232321 A232322 A232323 * A232325 A232326 A232327

Keyword

nonn

Author

Jaroslav Krizek, Nov 25 2013

Status

approved