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A243473
a(n) = numerator(sigma(n)/n) - denominator(sigma(n)/n) where sigma(n) = sum of divisors of n.
6
0, 1, 1, 3, 1, 1, 1, 7, 4, 4, 1, 4, 1, 5, 3, 15, 1, 7, 1, 11, 11, 7, 1, 3, 6, 8, 13, 1, 1, 7, 1, 31, 5, 10, 13, 55, 1, 11, 17, 5, 1, 9, 1, 10, 11, 13, 1, 19, 8, 43, 7, 23, 1, 11, 17, 8, 23, 16, 1, 9, 1, 17, 41, 63, 19, 13, 1, 29, 9, 37, 1, 41, 1, 20, 49, 16
OFFSET
1,4
COMMENTS
a(n) = 1 for n prime or perfect (A053813).
a(n) = A001065(n) when n is in A014567.
a(n) > n for n in A069057. - Michel Marcus, May 04 2016
LINKS
FORMULA
a(n) = A017665(n) - A017666(n).
MATHEMATICA
f[n_] := DivisorSigma[1, n]/n; Table[Numerator[f@ n] - Denominator[f@ n], {n, 76}] (* Michael De Vlieger, Sep 09 2015 *)
PROG
(PARI) a(n) = numerator(ab = sigma(n)/n) - denominator(ab);
KEYWORD
nonn
AUTHOR
Michel Marcus, Jun 05 2014
STATUS
approved