OFFSET
1,2
COMMENTS
See A245776 - numerator of (n / tau(n) - sigma(n) / n).
If n is an odd prime, a(n) = 2*n. - Robert Israel, Aug 01 2014
First deviation from A245785 (denominator of (n/tau(n) + sigma(n)/n)) is at a(300); a(300) = 75, A245785(300) = 25. Sequence of numbers n such that A245785(n) is not equal to a(n): 300, 768, 1452, 1764, 2100, 3468, 3900, 5376, 5700, 6084, 6348, 9075, 9300, ... See (Magma) [n: n in [1..10000] | (Denominator((n/(#[d: d in Divisors(n)]))+(SumOfDivisors(n)/n))) - (Denominator((n/(#[d: d in Divisors(n)]))-(SumOfDivisors(n)/n))) ne 0] - Jaroslav Krizek, Aug 15 2014
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
For n = 9; a(9) = denominator(9/tau(9) - sigma(9)/9) = denominator(9/3 - 13/9) = denominator(14/9) = 9.
MATHEMATICA
Table[Denominator[n/DivisorSigma[0, n] - DivisorSigma[1, n]/n], {n, 70}] (* Alonso del Arte, Aug 15 2014 *)
PROG
(Magma) [Denominator((n/(#[d: d in Divisors(n)]))-(SumOfDivisors(n)/n)): n in [1..100]]
(PARI) vector(150, n, denominator(n/numdiv(n) - sigma(n)/n)) \\ Derek Orr, Aug 01 2014
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Jaroslav Krizek, Aug 01 2014
STATUS
approved