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A088839 Numerator of sigma(4n)/sigma(n). 4
7, 5, 7, 31, 7, 5, 7, 21, 7, 5, 7, 31, 7, 5, 7, 127, 7, 5, 7, 31, 7, 5, 7, 21, 7, 5, 7, 31, 7, 5, 7, 85, 7, 5, 7, 31, 7, 5, 7, 21, 7, 5, 7, 31, 7, 5, 7, 127, 7, 5, 7, 31, 7, 5, 7, 21, 7, 5, 7, 31, 7, 5, 7, 511, 7, 5, 7, 31, 7, 5, 7, 21, 7, 5, 7, 31, 7, 5, 7, 127, 7, 5, 7, 31, 7, 5, 7, 21, 7, 5, 7, 31 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

Index entries for sequences related to sigma(n)

FORMULA

a(n) = (8*A006519(n)-1)/(1+2*A096268(n)). - Robert Israel, Nov 19 2017

MAPLE

f:= proc(n) local m;

  m:= padic:-ordp(n, 2);

  if m::odd then (2^(m+3)-1)/3 else 2^(m+3)-1 fi

end proc:

map(f, [$1..200]); # Robert Israel, Nov 19 2017

MATHEMATICA

k=4; Table[Numerator[DivisorSigma[1, k*n]/DivisorSigma[1, n]], {n, 1, 128}]

PROG

(PARI) A088839(n) = numerator(sigma(4*n)/sigma(n)); \\ Antti Karttunen, Nov 18 2017

CROSSREFS

For denominator see A088840.

Cf. A038712, A088837, A088838, A088841, A080278, A000203.

Cf. A006519, A096268.

Sequence in context: A195348 A072449 A263770 * A111769 A111513 A280722

Adjacent sequences:  A088836 A088837 A088838 * A088840 A088841 A088842

KEYWORD

easy,nonn,frac

AUTHOR

Labos Elemer, Nov 04 2003

EXTENSIONS

Typo in definition corrected by Antti Karttunen, Nov 18 2017

STATUS

approved

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Last modified July 16 12:19 EDT 2019. Contains 325079 sequences. (Running on oeis4.)