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 A054024 Sum of the divisors of n reduced modulo n. 44
 0, 1, 1, 3, 1, 0, 1, 7, 4, 8, 1, 4, 1, 10, 9, 15, 1, 3, 1, 2, 11, 14, 1, 12, 6, 16, 13, 0, 1, 12, 1, 31, 15, 20, 13, 19, 1, 22, 17, 10, 1, 12, 1, 40, 33, 26, 1, 28, 8, 43, 21, 46, 1, 12, 17, 8, 23, 32, 1, 48, 1, 34, 41, 63, 19, 12, 1, 58, 27, 4, 1, 51, 1, 40, 49, 64, 19, 12, 1, 26, 40 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS If a(n) = 0, then n is a multiply-perfect number (A007691). - Alonso del Arte, Mar 30 2014 LINKS Antti Karttunen, Table of n, a(n) for n = 1..65537 (first 1000 terms from T. D. Noe, terms 1001..20000 from Alois P. Heinz). Walter Nissen, Abundancy : Some Resources. FORMULA a(n) = sigma(n) mod n. a(p) = 1 for p prime. EXAMPLE a(12) = 4 because sigma(12) = 28 and 28 == 4 (mod 12). a(13) = 1 because 13 is prime. a(14) = 10 because sigma(14) = 24 and 24 == 10 (mod 14). MAPLE with(numtheory): seq(sigma(i) mod i, i=1..100); MATHEMATICA Table[Mod[DivisorSigma[1, n], n], {n, 80}] (* Alonso del Arte, Mar 30 2014 *) PROG (Haskell) a054024 n = mod (a000203 n) n -- Reinhard Zumkeller, Mar 23 2013 (PARI) a(n)=sigma(n)%n \\ Charles R Greathouse IV, Nov 04 2014 CROSSREFS Cf. A000203 (sigma), A005114 (untouchable numbers), A007691 (positions of 0's), A045768, A045769, A088834, A045770, A076496, A159907. Sequence in context: A055807 A213060 A272008 * A144644 A151509 A264434 Adjacent sequences: A054021 A054022 A054023 * A054025 A054026 A054027 KEYWORD nonn,easy AUTHOR Asher Auel (asher.auel(AT)reed.edu), Jan 19 2000 STATUS approved

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Last modified December 5 19:57 EST 2022. Contains 358588 sequences. (Running on oeis4.)