A158298 Denominators of averages of squares of the divisors of n.

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

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