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a(n) = (1/n) * Sum_{d|n} phi(n/d) * A000346(nd-1) for n>0. - Andrew Howroyd, Apr 02 2017
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(PARI)
a(n) = sumdiv(n, d, eulerphi(n/d)*(2^(2*d-1) - binomial(2*d-1, d)))/n; \\ Andrew Howroyd, Apr 02 2017
Andrew Howroyd, <a href="/A060404/b060404.txt">Table of n, a(n) for n = 0..200</a>
a(n) = (1/n) * Sum_{d|n} phi(n/d) * A000346(n-1). - Andrew Howroyd, Apr 02 2017
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max = 25; f[x_] := (1 - Sqrt[1 - 4*x])/(2*x) - 1; gf = Sum[(EulerPhi[k]/k)*Log[1 - f[x^k]], {k, 1, max}]; CoefficientList[ Series[-gf, {x, 0, max}], x] (* Jean-Fran�ois Alcover, Jan 21 2013 *)
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