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A088837 Numerator of sigma(2n)/sigma(n). Denominator see in A038712. 6
3, 7, 3, 15, 3, 7, 3, 31, 3, 7, 3, 15, 3, 7, 3, 63, 3, 7, 3, 15, 3, 7, 3, 31, 3, 7, 3, 15, 3, 7, 3, 127, 3, 7, 3, 15, 3, 7, 3, 31, 3, 7, 3, 15, 3, 7, 3, 63, 3, 7, 3, 15, 3, 7, 3, 31, 3, 7, 3, 15, 3, 7, 3, 255, 3, 7, 3, 15, 3, 7, 3, 31, 3, 7, 3, 15, 3, 7, 3, 63, 3, 7, 3, 15, 3, 7, 3, 31, 3, 7, 3, 15, 3 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

FORMULA

a(n) = 4*2^A007814(n)-1 = 4*A006519(n)-1 = A059159(n-1).

MATHEMATICA

k=2; Table[Numerator[DivisorSigma[1, k*n]/DivisorSigma[1, n]], {n, 1, 128}]

CROSSREFS

Cf. A038712, A088838-A088840, A080278.

2*A038712(n) + 1.

Sequence in context: A159566 A096385 A205723 * A201385 A186107 A019158

Adjacent sequences:  A088834 A088835 A088836 * A088838 A088839 A088840

KEYWORD

easy,nonn,frac

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Nov 04 2003

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Last modified February 15 16:21 EST 2012. Contains 205823 sequences.