how to define a function with loop

[Elim Qiu <elim.qiu@gmail.com>]

I'd like to define a function returns the decimal approximation of

(1^n+2^n+...+n^n)/(n^n)

In python i have

def tm(n,k):

    return exp(n*log((k+0.0)/n))

def sm(n,m):

    s = 0.0

    for j in range(m):

        k = n -j

        s += tm(n,k)

    return s

How do I put a loop inside of a definition of pari function?

Thanks