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
Examples
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.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Maple
with(numtheory): a:=n->numer(sum(1/phi(k)/sigma(k),k=1..n)): seq(a(n),n=1..35);
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Mathematica
Accumulate[Table[1/(EulerPhi[n]DivisorSigma[1,n]),{n,30}]]//Numerator (* Harvey P. Dale, Jun 19 2023 *)
Comments