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A158275
Denominators of antiharmonic means of divisors of n.
3
1, 3, 2, 1, 3, 6, 4, 3, 1, 9, 6, 2, 7, 12, 6, 1, 9, 3, 10, 1, 8, 18, 12, 6, 1, 21, 2, 4, 15, 18, 16, 3, 12, 27, 12, 1, 19, 6, 14, 9, 21, 24, 22, 2, 3, 36, 24, 2, 1, 1
OFFSET
1,2
COMMENTS
Numbers k such that sigma_2(k)/sigma_1(k) = A001157(k)/A000203(k) are integers are in A020487.
LINKS
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
Cf. A001157, A000203, A020487, A158274 (numerators).
Sequence in context: A325531 A115215 A335012 * A147750 A089942 A097409
KEYWORD
nonn,frac
AUTHOR
Jaroslav Krizek, Mar 15 2009
STATUS
approved