Re: [Reduce-algebra-developers] expansion of gamma function

[Rainer S. <rai...@gm...>]

On Sat, 10 Oct 2015 at 20:38 +0600, Andrey G. Grozin wrote:

 > Can't
 > 
 > log(gamma(1+x)) = - euler_gamma*x + sum((-1)^n*zeta(n)/n*x^n,n,2,infinity)
 > 
 > be used by taylor and/or tps, to calculate the series for gamma(1+x) as the
 > exponent of the known series?

Yes, you're right. Thanks for pointing it out.

However, it means that gamma, psi and friends must be treated specially. I had 
hoped to avoid that.

In addition, the above formula doesn't help for the expandsion of gamma(f(x)) 
where f(x) is some non-trivial, but well known function, like gamma(x^2-x^3) .

 > By the way, why, after loading specfn and sfgamma, psi(1) is not simpilfied
 > to -euler_gamma?

Purely historical. I'll see that rules for psi(1) and psi(1/2) are added.

  Rainer