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A158298
Denominators of averages of squares of the divisors of n.
3
1, 2, 1, 1, 1, 2, 1, 4, 3, 2, 1, 1, 1, 2, 1, 5, 1, 6, 1, 1, 1, 2, 1, 4, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 1, 3, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 4, 1, 2, 1, 1, 1, 2, 3, 7, 1, 2, 1, 1, 1, 2, 1, 12, 1, 2, 1, 1, 1, 2, 1, 5, 5, 2, 1, 1, 1, 2
OFFSET
1,2
COMMENTS
Average of squares of the divisors of n = A001157(n)/A000005(n).
Iff a(n) = 1, n is in A020486.
LINKS
MATHEMATICA
Array[Denominator[DivisorSigma[2, #]/DivisorSigma[0, #]] &, 100] (* Amiram Eldar, Jul 15 2019 *)
PROG
(PARI) a(n) = denominator(sigma(n, 2)/numdiv(n)) \\ Michel Marcus, Jun 13 2013
CROSSREFS
Cf. A001157, A000005, A020486, A158299 (for numerators).
Sequence in context: A051119 A159269 A186728 * A009191 A229969 A260909
KEYWORD
nonn,frac
AUTHOR
Jaroslav Krizek, Mar 15 2009
EXTENSIONS
Data corrected and extended by Amiram Eldar, Jul 15 2019
STATUS
approved