OFFSET
1,2
COMMENTS
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..10000
FORMULA
Antiharmonic mean of divisors of number n = Product (p_i^e_i) is sigma_2(n)/sigma_1(n) = A001157(n)/A000203(n) = Product ((p_i^(e_i+1)+1)/(p_i+1)).
a(A020487(n)) = 1. - Amiram Eldar, Nov 21 2022
EXAMPLE
Antiharmonic means of divisors of n>=1: 1, 5/3, 5/2, 3, 13/2, 25/6, ...
MATHEMATICA
Table[Denominator[DivisorSigma[2, n]/DivisorSigma[1, n]], {n, 50}] (* Ivan Neretin, May 22 2015 *)
PROG
(PARI) a(n) = denominator(sigma(n, 2)/sigma(n)); \\ Amiram Eldar, Nov 21 2022
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Jaroslav Krizek, Mar 15 2009
STATUS
approved