OFFSET
1,2
COMMENTS
a(n) = 1 when n is listed in A003601, a(n) > 1 when n is listed in A049642. - Alonso del Arte, Jan 31 2006
a(A069081(n)) = 2. - Bernard Schott, Sep 19 2019
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
EXAMPLE
a(12)=3 since the 6 divisors of 12 are 1, 2, 3, 4, 6 and 12 and 1+2+3+4+6+12=28 and 28/6=14/3.
MAPLE
with(numtheory): seq(denom(sigma(n)/tau(n)), n=1..70) ; # Zerinvary Lajos, Jun 04 2008
MATHEMATICA
Denominator[Table[(Plus @@ Divisors[n])/Length[Divisors[n]], {n, 70}]] (* Alonso del Arte, Feb 24 2006 *)
PROG
(Haskell)
import Data.Ratio ((%), denominator)
a057021 n = denominator $ a000203 n % a000005 n
-- Reinhard Zumkeller, Jan 06 2012
(PARI) a(n) = denominator(sigma(n)/numdiv(n)); \\ Michel Marcus, Apr 12 2016
(Magma) [Denominator(SumOfDivisors(n)/#Divisors(n)):n in [1..100]]; // Marius A. Burtea, Sep 08 2019
CROSSREFS
KEYWORD
frac,nonn
AUTHOR
Henry Bottomley, Jul 21 2000
STATUS
approved