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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. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
The first 5 sums are: 1,4/3,35/24,257/168,11/7.
LINKS
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
Sequence in context: A220256 A220320 A261186 * A174436 A145607 A188527
KEYWORD
frac,nonn
AUTHOR
Emeric Deutsch, Mar 12 2005
STATUS
approved

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Last modified March 28 08:22 EDT 2024. Contains 371236 sequences. (Running on oeis4.)