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A065915 Numerator of sigma(8*n^2)/sigma(4*n^2). 2
15, 63, 15, 255, 15, 63, 15, 1023, 15, 63, 15, 255, 15, 63, 15, 4095, 15, 63, 15, 255, 15, 63, 15, 1023, 15, 63, 15, 255, 15, 63, 15, 16383, 15, 63, 15, 255, 15, 63, 15, 1023, 15, 63, 15, 255, 15, 63, 15, 4095, 15, 63, 15, 255, 15, 63, 15, 1023, 15, 63, 15, 255, 15, 63 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The sequence is not periodic, values of numerators are always -1+2^s.

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

EXAMPLE

sigma(72)/sigma(36) = 15/7.

MATHEMATICA

Table[Numerator[DivisorSigma[1, 8n^2]/DivisorSigma[1, 4n^2]], {n, 70}] (* Harvey P. Dale, Mar 21 2018 *)

PROG

(PARI) for (n=1, 1000, a=numerator(sigma(8*n^2)/sigma(4*n^2)); write("b065915.txt", n, " ", a)) \\ Harry J. Smith, Nov 04 2009

(PARI) a(n)=2^(2*valuation(n, 2)+4)-1 \\ Charles R Greathouse IV, Nov 17 2015

CROSSREFS

Cf. A000203.

Sequence in context: A219296 A067572 A066584 * A062965 A157968 A141759

Adjacent sequences:  A065912 A065913 A065914 * A065916 A065917 A065918

KEYWORD

nonn,easy

AUTHOR

Labos Elemer, Nov 28 2001

STATUS

approved

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Last modified January 20 12:19 EST 2019. Contains 319330 sequences. (Running on oeis4.)