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A054024 Sum of divisors of n reduced modulo n. 36
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

T. D. Noe, Table of n, a(n) for n=1..1000

Walter Nissen, Abundancy : Some Resources

FORMULA

a(n) = A000203(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

CROSSREFS

Cf. A000203, A007691, A045768, A045769, A088834, A045770, A076496, A159907.

Sequence in context: A055807 A213060 A205099 * A144644 A151509 A151511

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 October 25 13:39 EDT 2014. Contains 248541 sequences.