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