\\% Conversion of power series of a hypergeometric function to a continued fraction.
\\ Author: Joerg Arndt
\\ License: GPL version 3 or later
\\ online at http://www.jjj.de/pari/
\\ version: 2011-January-19 (12:50)

read("contfrac.gpi");

hyper2cf(va, vb, n, z='z)=
\\ convert hypergeom(va,vb,z) into a continued fraction
{
    local(cfa, cfb, m);
    n += 2;
    cfa = vector(n);
    cfb = vector(n);
    cfa[1] = 0;    cfa[2] = 1;
    cfb[1] = 1;    cfb[2] = 1;
    for (k=3, n,
        m = 1/(k-2);  \\ hidden lower parameter 1:  (n-2) == 1+(n-3)
        m *= prod(j=1, #va, va[j]+(k-3));  \\ upper parameters
        m /= prod(j=1, #vb, vb[j]+(k-3));  \\ lower parameters
        m *= z;  \\ argument
        cfa[k]=(m+1);
        cfb[k]=-m;
    );
    return( [cfa, cfb] );
} /* ----- */

\\ ==== end of file ====