Friday, 25 January 2008

nt.number theory - A product of gamma values over the numbers coprime to n.

Denote f(n)=prodn1k=1Gammaleft(fracknright)

and F(n)=prod1leklen1,kperpnGammaleft(fracknright)

We have f(n)=prodd|nF(n) and therefore by Mobius inversion F(n)=prodd|nf(d)mu(n/d)



By the multiplication theorem we have f(n)=frac1sqrtn(2pi)fracn12, so if n is not a prime power F(n)=prodd|nleft(frac1sqrtd(2pi)fracd12right)mu(n/d)=(2pi)frac12varphi(n)


The formula F(n)=sqrtvarphi(n)+1f(varphi(n)+1) follows.

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