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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 (list; graph; refs; listen; history; text; internal format)
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

Amiram Eldar, Table of n, a(n) for n = 1..10000

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

Adjacent sequences:  A158295 A158296 A158297 * A158299 A158300 A158301

KEYWORD

nonn,frac

AUTHOR

Jaroslav Krizek, Mar 15 2009

EXTENSIONS

Data corrected and extended by Amiram Eldar, Jul 15 2019

STATUS

approved

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Last modified May 12 04:27 EDT 2021. Contains 343810 sequences. (Running on oeis4.)