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A232324 n(n+1)/2 modulo sigma(n). 9
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 11 18:01 EDT 2020. Contains 335652 sequences. (Running on oeis4.)