A104526 Numerator of sum(1/(phi(k)sigma(k)),k=1..n), where phi(k) is the totient function and sigma(k) is the sum of the divisors function.

1, 4, 35, 257, 11, 271, 183, 2773, 36329, 109897, 110443, 27757, 55709, 37291, 49873, 1549703, 13975537, 14010257, 2806565, 2811401, 5631265, 9400487, 103518197, 103642321, 103738417, 311569891, 311818139, 312084119, 312296903, 312607213

Offset

1,2

Comments

The first 5 sums are: 1,4/3,35/24,257/168,11/7.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

a(3)=35 because phi(1)*sigma(1)+phi(2)*sigma(2)+phi(3)*sigma(3)=1/(1*1)+1/(1*3)+1/(2*4)=35/24.

Maple

with(numtheory): a:=n->numer(sum(1/phi(k)/sigma(k), k=1..n)): seq(a(n), n=1..35);

Mathematica

Accumulate[Table[1/(EulerPhi[n]DivisorSigma[1, n]), {n, 30}]]//Numerator (* Harvey P. Dale, Jun 19 2023 *)

Crossrefs

Cf. A104527, A093827.

Sequence in context: A220256 A220320 A261186 * A174436 A145607 A188527

Adjacent sequences: A104523 A104524 A104525 * A104527 A104528 A104529

Keyword

frac,nonn

Author

Emeric Deutsch, Mar 12 2005

Status

approved