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A232324 n(n+1)/2 modulo sigma(n). 11
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
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
Sequence in context: A166994 A059083 A207626 * A124931 A210226 A209163
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Nov 25 2013
STATUS
approved

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Last modified April 14 04:54 EDT 2024. Contains 371655 sequences. (Running on oeis4.)